GB2486278A

GB2486278A - Rotating guide means for discharging particulate materials

Info

Publication number: GB2486278A
Application number: GB1021009.4A
Authority: GB
Inventors: George Arthur Willacy; Paul Willacy
Original assignee: GAW UK Ltd
Current assignee: GAW UK Ltd
Priority date: 2010-12-10
Filing date: 2010-12-10
Publication date: 2012-06-13
Also published as: GB201021009D0

Abstract

An apparatus for permitting controlled release of flowable particulate material comprises a chamber 20 for temporarily housing the particulate material, an outlet channel for exit of the material from the chamber at least partly under the action of gravity A. Guiding means are positioned in outlet channel 22 for assisting passage of the particulate material. The guiding means comprise elongate fingers 26a-e arranged on shaft 24a to rotate about a first axis extending transversely across channel 22, and second elongate fingers 28a-e arranged on a shaft 24b to rotate about a second axis extending transversely across channel 22. The axes are in the same direction but are laterally displaced from each other. The fingers on the respective shafts may rotate in opposite directions and may interdigitate. The apparatus may be a pyrolysis plant.

Description

Apparatus for assisting flow of particulate materials

Field of the invention

The present application relates to apparatus for assisting flow of particulate materials, in particular to apparatus for assisting flow of particulate materials along ducts or channels, under the action of gravity.

Background to the invention

Many processes are known in which particulate materials held within a chamber are caused to exit the chamber along an outlet channel, under the action of gravity. For example, in downdraft gasification apparatus, such as that described in GB24531 11 BI, ash residue from the gasification process collects in a chamber at the base of the gasification apparatus and exits the apparatus under the action of gravity, along an outlet channel that delivers the ash residue to e.g. a conveyor belt. Typically, the outlet channel comprises an airlock screw auger system.

US 4659340 discloses a pressurised downdraft gasifier in which a gasifying chamber communicates with an ash-collection chamber along a throated zone. A cylindrical grate bar assembly is positioned below the gasifying chamber and depends into the ash-collection chamber. The cylindrical grate bar allows passage of gas products through the grate bar assembly. A grate bar clearing assembly has grate clearing blades extending laterally from a shaft, to free the grate bars of clinkers that may be deposited between them.

In systems in which are configured to allow particulate materials to flow through an outlet channel under the action of gravity, the flow of the materials may be difficult to control or regulate.

Summary of invention

Therefore, at its most general, the present invention provides apparatus for assisting and/or regulating the controlled release of flowable materials from an outlet channel.

In a first aspect, the present invention provides apparatus for permitting controlled release of flowable particulate material, comprising a chamber for temporarily housing the particulate material and an outlet channel for allowing exit of the particulate material at least partly under the action of gravity, wherein guiding means are positioned in the outlet channel, the guiding means being for assisting passage of the particulate material through the outlet channel, the guiding means comprising at least one first elongate finger arranged to rotate about a first axis extending transversely across the channel, and at least one second elongate finger arranged to rotate about a second axis that extends transversely across the channel, along the same direction as the first axis, and laterally placed from the first axis.

Typically, the apparatus is part of a pyrolysis plant that is adapted to pyrolyse and gasify material descending through the apparatus. In this case, the chamber may house ash residue from the pyrolysis and gasification processes. The pyrolysis plant may be configured to process e.g. refuse-derived fuel (RDF) and/or biomass.

Operation of the guiding means may allow increased control over the flow of particles through the outlet channel, for example, assisting smooth particle flow, so as to reduce the level of particulate material inside the chamber in an even fashion. This may also assist control of any reaction occurring within the chamber. For example, in the case that the apparatus is part of a pyrolysis plant, the gasification reaction may proceed in a more stable fashion and/or the level of carbon in the ash residue may be controlled more closely.

By helping to control flow of particles through the outlet channel, the guiding means may allow increased control of the pressure within the apparatus. It is known that, for example in a pyrolysis plant, the gasification characteristics may depend strongly on the pressure within the apparatus.

Operation of the guiding means may help to reduce bridging effects upstream of the outlet channel. Such bridging may be caused e.g. by compaction of the particulate material resulting from the weight of material above it, and may have the effect of inhibiting the discharge of material through the outlet channel. Such bridging effects may also result in increased pressure within the apparatus, due to disrupted flow of material and/or reduced control over the pressure of the apparatus.

In addition, operation of the guiding means may help to break up clinker pieces, and so reduce blockage of the outlet channel. Such clinker pieces are typically formed in e.g. pyrolysis plants, when the plant is used to process waste materials or when it experiences a period of inactivity. In this case, the clinker pieces are made up of heavily compacted, partly fused ash residue, and so disrupt particle flow.

Typically, the apparatus includes a power source, such as a motor, that is adapted to allow intermittent operation of the guiding means to assist and/or regulate flow of particulate material along the outlet channel.

Typically, the first and second fingers are arranged to rotate in opposite directions. For example, the at least one first finger may rotate in a clockwise direction and the at least one second finger in an anticlockwise direction. This arrangement may allow the respective first and second fingerers to travel in substantially similar directions when they are sweeping through a central portion of the channel, thus guiding the particulate material along the length of the channel.

In general, the guiding means comprise a series of the first fingers and a series of the second fingers. Each such series is distributed along the direction defined by the first and second axes, the series of second fingers being laterally displaced from the series of first fingers. Thus, the guiding means may comprise a sequence of first fingers, each first finger having a respective position along the first axis, and a sequence of second fingers, each second finger having a respective position along the second axis.

Effectively, therefore, the guiding means may comprise several pairs of first and second fingers, the pairs being positioned in sequence across the width of the channel.

However, the guiding means do not necessarily comprise equal numbers of first and second fingers.

In this case, the array of first fingers may be staggered relative to the array of second fingers. That is, the positions of first fingers may alternate with the positions of second fingers across the width of the channel, that is, along the direction defined by the first and second axes. This arrangement may allow the series of first fingers to cooperate with the array of second fingers to assist the passage of particulate material through the channel.

Typically, the first and second fingers are elongate in shape and extend laterally from the first and second axes, respectively. In general, the first and second fingers extend laterally from respective first and second shafts, the first and second shafts being positioned lengthwise along the first and second axes respectively.

In this case, it is preferred that the series of first fingers is arranged to interdigitate with the series of second fingers. That is, when viewed along the direction of the first and second axes, the area swept out by at least one first finger during rotation about the first axis overlaps with the area swept out by at least one second finger during rotation about the second axis. However, it is not necessary that the series of first fingers interdigitates with the series of second fingers along its entire length.

Optionally, the guiding means comprises an internal passageway for delivering fluid into the outlet channel. Such fluid may be e.g. air or steam and may be provided to promote a chemical transformation of the particulate material. For example, in the case that the apparatus is part of a pyrolysis plant and the particulate material is ash residue, air and/or steam may be delivered along the internal passageway to promote increased conversion of carbon retained within this ash residue. This may be achieved through a secondary water shift reaction (that is, an additional water shift reaction to the one occurring upstream of the outlet channel). Such an arrangement may assist in compliance of the pyrolysis plant with regulations limiting the carbon content of ash residue.

The internal passageway may comprise one or more ducts provided in a shaft to which one of the first or second fingers is attached. Optionally, the passageway may extend into one or several of the first or second fingers.

By providing an internal passageway within the guiding means, it may be possible to introduce a fluid evenly into the particulate material, while it is flowing along the outlet channel. This delivery mechanism may enhance the reaction between the fluid and the particulate material.

Detailed description

The invention will now be described by way of example with reference to the following Figures in which: Figure 1 is a fragmentary sectional view of a gasification plant according to an embodiment of the invention; and Figure 2 shows a plan view of the outlet channel of the plant of Fig. 1.

Figure 1 shows a downdraft gasification apparatus or pyrolysis plant 10. Heated air and fuel are supplied through inlets (not shown) at the top of the gasification apparatus and travel downwards under gravity, as shown by direction arrow A. The heated air and fuel pass through a first chamber 12. Chamber 12 tapers inwardly in the direcflon of travel of the heated air and fuel, to provide a throat or restriction 14.

Chamber 12 provides a pyrolysis zone 16 and an oxidation zone 18, the oxidation zone being located in the throat 14 of chamber 12, below the pyrolysis zone 16.

Ash residue from the oxidation process is temporarily collected in a second chamber 20, and exits the second chamber 20 under the action of gravity, through outlet channel 22.

On leaving the second chamber 20, the ash residue drops onto a conveyor screw 24 and is transported away from the gasification apparatus 10.

Figure 2 shows a detailed plan view of the outlet channel 22 of the gasification apparatus of Figure 1. However, the arrangement shown in Figure 2 may also be used in conjunction with other apparatus in which particulate material is held.

Outlet channel 22 comprises a first shaft 24a and a second shaft 24b, each shaft extending transversely across the channel, along direction B. The second shaft 24b is laterally dispiaced from the first shaft 24a. Each shaft 24a,24b is supported by pillar bearings 25a,25b, such that it is able to rotate about a respective rotation axis extending transversely across channel 22 (that is, extending along direction B).

Each shaft 24a, 24b is provided with a respective series 26a-e, 28a-d of spaced elongate fingers. The fingers on each shaft extend in a lateral direction of the shafts 24a,24b.

The two finger series 26a-e, 28a-d are staggered. That is, in a direction of travel defined by the orientation of shafts 24a,24b (that is, in direction B), fingers from the first series 26a-e alternate with fingers from the second series 28a-d.

The two finger series 26a-e, 28a-d interdigitate. That is, when viewed along the direction defined by the orientation of shafts 24a,24b (in direction B), the volume swept out by fingers 26b,c,d during rotation about shaft 24a overlaps with the volume swept out by fingers 28a,b,c,d during rotation about shaft 24b.

Each finger in each series 26a-e,28a-d is positioned symmetrically on its respective shaft 24a,24b. That is, each finger has portions of equal length extending on either side of the respective shaft 24a,24b.

The longest fingers in each series of fingers are at the centre of the series. The length of the fingers decreases with increasing distance from the centre of the series.

Shafts 24a,24b and fingers 26a-e and 28a-d are hollow to allow passage of fluid along each respective shaft, and into and along the fingers connected to the shafts. That is, each shaft 24a,24b has an internal duct extending along its length, the duct being in fluid communication with the ducts provided in the fingers mounted on that shaft. Each shaft and finger is provided with a plurality of apertures 30 to allow exit of the fluid into the bore of the channel 22.

Motor 32 drives shaft 24a, while gearing 34 causes shaft 24b to rotate in an opposite direction to that of shaft 24a. For example, shaft 24a may rotate in a clockwise direction, while shaft 24b may rotate in an anticlockwise direction.

When in use, motor 32 operates to drive intermittent, synchronous rotation of shafts 24a and 24b. This rotation aids the passage of ash residue along channel 22 and reduces the extent of compaction and consequent bridging of char upstream of channel 22. The rotation of the shafts 24a,24b may also aid the break-up of clinker that may form in the outlet channel, for example, when the gasification apparatus is being used to process waste material, or when the gasification apparatus is re-started after a period of inactivity.

The ducts extending along the shafts 24a,24b and the fingers 26a-e and 28a-d allow fluid such as air and/or steam to be introduced into the base of the gasification apparatus, to promote further conversion of any carbon remaining in the fuel. The distribution of the apertures allows e.g. the air and/or steam to be introduced throughout any remaining fuel.

Claims

Claims 1. An apparatus for permitting controlled release of flowable particulate material, the apparatus comprising a chamber for temporarily housing the particulate material and an outlet channel for allowing exit of the particulate material from the chamber at least partly under the action of gravity, wherein guiding means are positioned in the outlet channel, the guiding means being for assisting passage of the particulate material through the outlet channel, the guiding means comprising at least one first elongate finger arranged to rotate about a first axis that extends transversely across the channel, and at least one second elongate finger arranged to rotate about a second axis that extends transversely across the channel, along the same direction as the first axis, and laterally displaced from the first axis.
2. Apparatus according to claim 1, wherein the guiding means further comprise: a first shaft that is disposed along the first axis, the at least one first finger extending from the first shaft; and a second shaft that is disposed along the second axis, the at least one second finger extending from the second shaft.
3. Apparatus according to claim 1 or claim 2, wherein the first and second fingers are arranged to rotate in opposite directions.
4. Apparatus according to any preceding claim, wherein the guiding means comprises a series of the first fingers spaced along the first axis and a series of the second fingers, spaced along the second axis.
5. Apparatus according to claim 4, wherein the series of first fingers is staggered relative to the array of second fingers, such that aiong the direction defined by the first and second axes first fingers are arranged to interdigitate with second fingers.
6. Apparatus according to any preceding claim, wherein the guiding means includes an internal passageway for allowing delivery of a fluid into the outlet channel.
7. A pyrolysis plant for pyrolysis and gasification of solid material descending therethrough, the plant including apparatus according to any of claims 1 to 8 at a gravity-fed outlet end of thereof.
8. A method of assisting controlled release of particulate material from a chamber, comprising the steps of: providing an apparatus according to any one of claims 1 to 6, and rotating the first and second finger members about the respective first and second axes to assist exit of the particulate material from the chamber.
9. A method according to claim 8, wherein the first and second finger members are rotated intermittently.
10. A method according to claim 8 or claim 9, wherein the apparatus provides an outlet end for a pyrolysis plant in which material descending therethrough is pyrolysed and gasified.