GB2360230A

GB2360230A - Apparatus for removing dirt and debris from particulate material

Info

Publication number: GB2360230A
Application number: GB0106406A
Authority: GB
Inventors: Patrick Gerrard Sheehan
Original assignee: Catalyst Handling Res & Engine
Current assignee: Catalyst Handling Res & Engine
Priority date: 2000-03-14
Filing date: 2001-03-14
Publication date: 2001-09-19
Also published as: GB0106406D0

Abstract

Particulate handling apparatus suitable for removing debris from particulate material, and a method of removing debris from particulate material. The handling apparatus includes a hopper 2 having an inlet port 4 and an outlet port 6, and a cleaning gas introduction means 10. The cleaning gas introduction means is configured to direct at least one stream of cleaning gas at particulate material passing from the inlet port 4 to the outlet port 6. The stream of cleaning gas being directed and of sufficient velocity so as to substantially separate dust and debris from the particulate material. The apparatus has particular application in cleaning pellet-form catalyst.

Description

2360230 Particulate Handling Apparatus The present invention relates to

particulate handling apparatus, and in particular, apparatus for handling catalysts in the form of pellets or the like, and a method of removing debris from the particulate material.

Catalyst pellets are frequently used in reactors to enhance or cause chemical reactions within the reactors. The reactors are generally of substantial size and either constructed in situ, or transported whilst empty. Once the reactor is in the correct location and fully constructed, it is loaded with catalyst prior to use of the reactor commencing.

is Once the catalyst has been in the reactor f or a period of time, it is often desired to clean the catalyst, to treat the catalyst so as to renew it, or, simply to allow the catalyst to be re-bedded to overcome any problems caused by settling and subsequent compaction, of the catalyst. All of these treatments generally involve removing the catalyst from the reactor.

Each time the catalyst pellets are moved, and in particular, when they are being transported over long distances, it is inevitable that the catalyst will generate some dust and debris. This is because the catalyst moves and vibrates causing the catalyst pellets to abrade each other.

It is undesirable that the dust and debris generated by the abrasion be loaded into a reactor. This is because such dust and debris can cause a number of problems. For example, the dust can cling to and coat the pellets of the catalyst thus reducing their efficiency through loss of surface contact with the substance being passed through the reactor. Alternatively, and/or in addition to the first problem, dust and debris in the reactor may fill the cavities between the pellets, this will increase the pressure drop across the bed of catalyst. This leads to an increased pressure being required to push the substance being reacted through the catalyst bed.

In the past, problems arising from dust and debris have is been minimised by screening the catalyst pellets when they are removed from a reactor and prior to being placed in a reactor. Such screening may lead to further damage to the catalyst pellets being screened, and may, depending upon the nature of the catalyst, be dangerous.

Therefore, it is an aim of the present invention to alleviate at least some of the disadvantages identified above. It is a further aim of the present invention to provide apparatus for substantially separating dust and debris from the pellets whilst either loading the reactor or unloading the reactor. It is a further aim of the present invention to provide a method of substantially separating dust and/or debris from the pellets whilst either loading or unloading the reactor.

Therefore, according to a first aspect of the present invention there is provided handling apparatus including a hopper having a particulate material inlet port and a particulate material outlet port, and cleaning gas introduction means conf igured to direct at least one stream of cleaning gas at particulate material passing from the particulate material inlet port to the particulate material outlet port, the at least one stream of cleaning gas being directed and of sufficient velocity so as to substantially separate dust and debris from the particulate material.

The apparatus of the present invention may separate both loose dust and debris (hereafter known as debris) that is entrained with the particulate material, and debris located on the surface of the particulate material.

It is particularly preferred that the particulate material is in the form of a pellet, a shaped or formed body, or the like.

Typically, the particulate material is a catalyst, preferably in the form of a pellet.

Separating the debris from the particulate material by way of a cleaning gas stream impacting on the particulate material is particularly advantageous in that the cleaning gas does not physically damage the particulate material by abrasion. Furthermore, the apparatus of the present invention can be configured as a sealed unit which significantly lessens the dangers associated with handling of catalysts.

In a particularly preferred embodiment of the present invention, the particulate material inlet port and the particulate material outlet port are arranged such that particulate material is unsupported by physical means for at least part of the time in which particulate material passes from the inlet port to the outlet port. Such an arrangement may include the particulate material falling under the force of gravity for example. Such a fall might be in a vertical direction or may be in a parabola.

It is most preferred that at least one stream of cleaning gas impacts upon the particulate material when it is unsupported by any physical means. This allows the cleaning gas to circulate fully around the particulate is material and thus maximise the debris separated from the particulate material.

Once the debris has been substantially separated from the particulate material, it is desirable that the debris be moved away from the particulate material. To achieve this it is preferred that the average direction of travel of the particulate material and the average direction of flow of the cleaning gas stream are substantially not parallel when the cleaning gas stream impacts the particulate material.

The cleaning gas introduction means and the hopper are preferably so constructed and configured that this occurs.

Most preferably, the angle between the direction of travel of the particulate material and the direction of flow of at least one cleaning gas stream when the stream impacts the particulate material is in the range of 900 to 1800, that is the directions of travel of the particulate material and at least one stream of cleaning gas are at least partially against each other. This has the advantage that such flow increases the turbulence of the interaction between the cleaning gas and the particulate material. The turbulence achieved increases the ability of the cleaning gas to separate debris from the particulate material.

Typically the cleaning gas introduction means comprises a gas source, at least one gas stream formation means and, at least one conduit for transporting the gas from the gas source to each gas stream formation means and it is further preferred that the cleaning gas introduction means further is includes means for adjusting the rate of flow of gas from the gas source to each gas stream formation means.

The means for adjusting the rate of flow of gas exiting one or more gas stream formation means may be gas flow control means known to a person skilled in the art. Particularly preferred gas flow control means are volumetric control means for use when the gas remains at a constant pressure, or pressure control means.

The cleaning gas may be air, nitrogen or any other gas appropriate for the particulate material being handled (for example a gas which does not react with the particulate material).

In one embodiment of the present invention where each gas stream formation means forms a stream of gas, each stream may have a different average direction of travel.

In a preferred embodiment of the present invention the cleaning gas stream formation means is a longitudinally extending manifold which is provided with at least one aperture passing through the wall of the manifold. The manifold is mounted on the inside face of the hopper so that each aperture through the wall of the manifold is so orientated that the streams of cleaning gas coming out of each aperture are directed toward the particulate material when the particulate material passes between the inlet port and outlet port.

Alternatively, the manifold may be mounted on an outside face of the hopper, and the hopper may be provided with at least one aperture through the wall of said hopper, each aperture corresponding to and in communication with an aperture in a side wall of the manifold.

In an alternative embodiment, the gas stream formation means may include a manifold, one of the walls of which is formed from a portion of a wall of the hopper. In this embodiment, the manifold is, as stated, formed partially from a wall of the hopper, and partially from a trough-like element, said trough-like element being fixed to the wall of the hopper in a gas-tight fashion.

Alternatively, at least one gas stream formation means may similarly be formed from an aperture through a side wall of a hopper to which may be connected a conduit supplying gas from the gas source.

In all of the cleaning gas stream formation means of the present invention. at least one aperture may be provided with a nozzle. The provision of a nozzle is particularly beneficial because it leads to a degree of control of the direction of the gas stream emerging from the gas stream formation means.

In one particularly preferred embodiment of the present invention the orientation of at least one of the nozzles is adjustable. The particular advantage of providing such a degree of adjustment is that the apparatus of the present invention may be fine tuned to give optimal performance by empirical methods. This is particularly beneficial because it is very difficult to theoretically model turbulent gas is flow such as may be expected to occur within the hopper of the present invention. It may be easier to empirically determine the optimal orientation of the nozzles by trial and error than by theoretical methods. Such empirical experimentation is optimally performed using pellets of similar weight and size to the catalyst intended to be moved. Said pellets optimally being of an inert, harmless material.

It is particularly preferred that the present invention is employed when handling entrained particulate material/gas mixtures. In such a circumstance, the hopper may be configured to widen out from the particulate material inlet port to a central chamber. The particulate material outlet port is below the central chamber (when the hopper is in the orientation in which it will be used). Such that at least one stream of cleaning gas impacts the pellets in the central chamber. The hopper is further provided with at least one gas outlet, said gas outlet being dimensioned and configured to permit entrainment gas, cleaning gas, and the debris separated from the pellets to exit from the hopper. In one embodiment each gas outlet means is connected to a suction means. The suction means may be a vacuum pump.

The or each gas outlet is preferably substantially in the region of the particulate material inlet port, and in such a position that particulate material from the inlet port would not, in normal use of the apparatus of the present invention, be expected to travel from the particulate is material inlet port to the or each gas outlet.

When operating the apparatus of the present invention, and in particular when the particulate material being conveyed through the particulate material inlet means in an entrainment gas, it is important that the pressure within the hopper is kept at a steady, desired level, which may be predetermined. This is achieved by controlling the ratio of the volume of gas/particulate material mixture entering via the particulate material inlet port and cleaning gas entering the hopper, and the rate of exit of gas from the hopper via the gas outlet means, and particulate material from the particulate material outlet. If there is an imbalance, then the pressure within the hopper will deviate from the desired pressure. This may cause the flow of the particulate material within the hopper to be disrupted and 9_ the separation of debris from the particulate material to occur at sub- optimal levels.

Furthermore, a careful balance has to be maintained between the volume of gas and entrained particulate material and the volume of the cleaning gas entering the hopper and the respective pressures of the gas/particulate material and the cleaning gas. If the cleaning gas is at a substantially higher pressure than that of the particulate material /entrained gas mixture, and this is not balanced by a difference in flow rate into the hopper, this can cause a back-up in the conduit leading to the particulate material inlet port which may cause blockages to occur. A preferred volume ratio of particulate material /entrainment gas mixture to cleaning gas in the f orm of gas streams at a higher pressure, is 15:1. Again, however, the optimal ratio is best determined empirically because of the complex nature of the gas flow within the hopper.

According to a further aspect of the present invention, there is provided a method of removing debris from particulate material, the method including directing at least one stream of gas at the particulate material, the stream of gas being so directed and of sufficient velocity so as to substantially separate debris from the particulate material.

It is particularly preferred that the method is performed using apparatus according to the first aspect of the present invention.

The present invention will be further explained by way of example only with reference to the accompanying drawings in which:

Figure 1 represents apparatus according to the present invention; and Figure 2 represents, schematically, the apparatus of Figure 1 in use.

Referring to Figure 1, a hopper (2) includes a pellet inlet port (4) and a pellet outlet port (6) between which is a void defined by hopper (2). Hopper (2)and the pellet ports (4) and (6) are so configured and positioned that is catalyst pellets entering the hopper through the inlet port (4) fall under the force of gravity toward the outlet port (6) and are funnelled towards said outlet port (6) by the walls of hopper (2) forming a funnel narrowing to outlet port (6).

Located on wall (8) of hopper (2) is a gas manifold (10) Gas manifold (10) is substantially "U" shapedin cross section and the free ends of the "U" are fixed to wall (8) in a gas tight fashion. The longitudinal ends of manifold (10) are sealed in a gas tight fashion, with one end being provided with a means (not shown) adapted to have a gas supply attached to said means, and to allow communication of gas into manifold (10) In the portion of wall (8) located between the ends of the "U" of manifold (10) are a number of apertures (not shown) which allow gaseous communication between the inside of manifold (10) and inside of hopper (2). Preferably, each aperture is provided with a nozzle which is adjustable for both direction and gas flow.

The manifold (10) is fixed to wall (8) in such a position that gas streams emanating from the apertures in wall (8) are in substantially the opposite direction to the direction of flow of the pellets.

Located vertically above pellet inlet (4) is gas outlet (12). Gas outlet (12) is adapted to be connected to a means for inducing sub-atmospheric pressure and a dust and debris filter means. Pellet inlet (4) and gas outlet means is (12) are so positioned relative to each other that it is not expected in the normal operation of hopper (2) that pellets entering the hopper (2) will be able to exit the hopper via gas outlet means (12).

With reference to Figures 1 and 2, when the apparatus of the present invention is to be used, for emptying a reactor (20), catalyst pellets (22) within reactor (20) are entrained with a conveyor gas by known means. The entrained gas/pellet mixture is then pumped along an appropriate conduit to the pellet inlet port(4) in the hopper (2). The pellets once they have passed through the inlet (4) fall in a parabola toward pellet outlet (6) following the path shown by arrow (24) At the same time, a cleaning gas is pumped into manifold (10) from a remote source (not shown). Said cleaning gas then passes through the apertures in wall (8) and is directed in streams via the nozzles toward the pellets falling from the pellet inlet port (4) toward the pellet outlet port (6). The cleaning gas buffets the pellets and causes any dust and debris entrained with the pellets or loosely attached to the surface of the pellets to separate from the pellets.

Gas outlet port (12) is in communication with a means for producing a subatmospheric pressure (not shown) and filter means. The means for producing sub-atmospheric pressure causes gas to flow out of hopper (2) via gas outlet (12).

The streams of cleaning gas emanating from manifold (10) are directed in the general direction of gas outlet (12); this combined with the sub-atmospheric pressure being applied to gas outlet (12) causes the mixture of entrained gas and dust and debris from the catalyst to exit the hopper via gas outlet means (12). Once the gas and dust and debris mixture has passed through gas outlet means (12), the gas and the dust and debris may be separated in a known fashion.

The velocity of the streams of cleaning gas may be adjusted by known pressure adjustment means (not shown) in the gas supply means. The greater the velocity of the gas streams, the greater the mass of a piece of debris that will be separated from the catalyst pellets by the cleaning gas.

As may be seen from the above, the present invention provides a means for cleaning particulate catalysts by way of "washing" with a cleaning gas thus avoiding unnecessary abrasion and thus damage to the catalyst. It is particularly advantageous where the catalyst is either toxic to human health or potentially volatile because the cleaning operation can take place under sealed conditions, thus protecting workers in the vicinity of the reactor.

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Claims

Claims:

1 Handling apparatus which include a hopper having a particulate material inlet port and a particulate material outlet port, and cleaning gas introduction means configured to direct at least one stream of cleaning gas at particulate material passing from the particulate material inlet port to the particulate material outlet port, the at least one stream of cleaning gas being directed and of sufficient velocity so as to substantially separate dust and debris from the particulate material.

2. Apparatus according to claim 1, wherein the is particulate material is in the form of a pellet, shaped or formed body, or the like.

3. Apparatus according to claim 1 or 2, wherein the particulate material is a catalyst, typically in pellet form.

4. Apparatus according to any of claims 1 to 3, which is configured as a sealed unit.

5. Apparatus according to any preceding claim, wherein the particulate material inlet port and the particulate material outlet port are arranged such that particulate material is unsupported by physical means for at least part of the time in which the particulate material is passing from the particulate -is- material inlet port to the particulate material outlet port.

6. Apparatus according to claim 5, wherein particulate 5 material entering the hopper via the particulate material inlet port is permitted to fall under the force of gravity from the particulate material inlet port to the particulate material outlet port.

7. Apparatus according to claim 6, wherein the particulate material falls in a substantially vertical direction or in a parabola.

8. Apparatus according to any preceding claim, wherein is the cleaning gas impacts upon the particulate material when it is unsupported by physical means.

9. Apparatus according to any preceding claim, wherein the average direction of travel of the particulate material and the average direction of flow of the cleaning gas stream are substantially not parallel when the cleaning gas stream impacts the particulate material.

10. Apparatus according to any preceding claim, wherein the particulate material travel in a first direction and the flow of at least one cleaning gas travels in a second direction, whereby the angle between the first direction and the second direction is substantially in the range of 900 to 18011.

11. Apparatus according to any preceding claim, wherein the cleaning gas is air, nitrogen or a gas which does not react with the particulate material.

12. Apparatus according to any preceding claim, wherein cleaning gas introduction means comprises a gas source, at least one gas stream formation means, and at least one conduit for transporting the gas from the gas source to each gas stream formation means.

13. Apparatus according to claim 12, where-in the cleaning gas introduction means further includes means for adjusting the rate of flow of gas from the gas source to each gas stream formation means.

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14. Apparatus according to claim 13, wherein the means for adjusting the rate of flow of gas exiting one or more gas stream formation means includes volumetric gas control means or pressure control means.

15. Apparatus according to any of claims 12 to 14, wherein each gas stream formation means forms a stream of gas.

16. Apparatus according to claim 15, wherein each stream has a different average direction of travel.

17. Apparatus according to claim 15 or 16, wherein the cleaning gas stream formation means is a longitudinally extending manifold which is provided with at least one aperture passing through the wall of the manifold.

18. Apparatus according to claim 17, wherein the hopper has an inside face which has the manifold attached thereto such that each aperture through the wall of the manifold is so orientated such that the streams of cleaning gas coming out of each aperture are directed toward the particulate material when they pass between the particulate material inlet port and particulate material outlet port.

19. Apparatus according to claim 17, wherein the manifold is on an outside face of the hopper, and the hopper is provided with at least one aperture through the wall of said hopper, each aperture corresponding to and in communication with an aperture in a side wall of the manifold.

20. Apparatus according to any of claims 12 to 19, wherein the gas stream formation means may include a manifold, one of the walls of which is formed from a portion of a wall of the hopper.

21. Apparatus according to claim 19, wherein the manifold is formed partially from a wall of the hopper, and partially from a trough-like element, said trough-like element being f ixed to the wall of the hopper in a gas-tight fashion.

22 Apparatus according to any of claims 12 to 21, wherein at least one gas stream formation means is formed from an aperture through a side wall of the hopper which has connected thereto a conduit supplying gas from the gas source.

23. Apparatus according to any of claims 16 to 20, wherein the cleaning gas introduction mans is further provided with a nozzle, preferably having an adjustable orientation.

24. Apparatus according to any preceding claim, wherein the hopper is configured to widen out from the particulate material inlet port to a central chamber, the particulate material outlet port being below the central chamber when the apparatus is in the orientation in which it will be used.

25. Apparatus according to any preceding claim, which is provided with at least one gas outlet.

26. Apparatus according to claim 25, wherein the or each gas outlet is substantially in the region of the particulate material inlet port.

27. Apparatus according to any preceding claim, wherein the hopper is maintained at a steady desired level (which is typically predetermined)

28. Apparatus according to claim 27 wherein the volume of gas and/or entrained particulate material entering the hopper via the particulate material inlet port and the cleaning gas entering the hopper via the gas inlet port, is controlled so as to maintain the hopper at the steady desired level.

29. A method of removing debris from particulate material which method includes directing at least one stream of cleaning gas at the particulate material, the stream of gas being so directed and of sufficient velocity so as to substantially separate from the particulate material.

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30. A method according to claim 29 which is performed using apparatus as defined in any of claims 1 to 23.

31. Apparatus substantially as described herein with reference to the accompanying drawings.