WO2005000715A1

WO2005000715A1 - Agitator for chanelling solid material, feeding system and gas producer with such an agitator

Info

Publication number: WO2005000715A1
Application number: PCT/EP2004/006898
Authority: WO
Inventors: Debra Jenkins; David Surplus; Kjell Holmgren; Bjorn Kjellstrom
Original assignee: Exus Energy Limited
Priority date: 2003-06-26
Filing date: 2004-06-24
Publication date: 2005-01-06
Also published as: GB0314881D0

Abstract

An agitator (10) comprising a hollow body (11) for channeling solid material, and means (14, 16) for imparting agitative motion to the body. The agitator (10) is particularly suited for use in a gas producer (12) that burns solid fuel and includes a feed hopper (20) for feeding the fuel into a combustion zone (22). The agitator is provided between the feed hopper and the combustion zone in order to channel said solid fuel from the feed hopper to the combustion zone. The application of agitative motion to the agitator body serves to prevent bridging in the solid fuel.

Description

AGITATOR FOR CHANELLING SOLID MATERIAL, FEEDING SYSTEM AND GAS PRODUCER WITH SUCH AN AGITATOR

FIELD OF THE INVENTION

5 The present invention relates to- agitators. The invention relates particularly, but not exclusively, to agitators for use with gas producers, including downdraft or updraft producers.

BACKGROUND TO THE INVENTION

10 Gas producers may use solid fuel comprising, for example, biomass, coal or waste material. Such fuel generally comprises a quantity, or mass, of elements such as chips, chunks, lumps, shavings, pellets, powder, briquettes or other granular or particulate material. Under normal atmospheric conditions, the fuel may be said 5 to comprise solid material, or bulk solid material. The fuel may take a natural form, for example nut shells, or may be processed to form units, for example wood chips briquettes, of any suitable size. Normally the fuel is loaded into a hopper and the lower end of the hopper feeds the fuel into a burn zone or combustion zone. A common problem is that, in a region (commonly known as 0 the pyrolysis zone) just above the combustion zone, high temperatures are present, and the fuel, when it reaches this region, tends to be converted, at least in part, to tar and therefore becomes sticky. This coagulation of the fuel tends to cause a blockage in the hopper or associated feed system. 5 Hence, in the pyrolysis zone, the normally discrete fuel elements tend to stick together and prevent the flow of the fuel from reaching the burn zone or combustion zone. This is commonly known as "bridging" and results when the fuel flows together, or coagulates, to form a bridge, and therefore a blockage, between the inner walls or other components of the feed mechanism (typically in0 an arch). Bridging can also occur higher up in the feed hopper, out of the pyrolysis zone and/or in the absence of high temperatures - a quantity of solid fuel elements may simply become jammed in the feed system. Bridging may occur for a number of reasons, for example the formation of tar in the pyrolysis zone of a gas producer; the size, shape and or orientation of the solid fuel elements relative to the dimensions of the volume through which the granular material is flowing; the surface ^"characteristics of the outer boundary of the volume through which the granular material is flowing; or swelling of the granular material due, for example, to the presence of heat.

Conventionally, to solve this problem, gas producers include an agitator for agitating the solid fuel elements and preventing them from forming a blockage, particularly in the pyrolysis zone and at the entrance of the combustion zone. Typically, agitators take the form of stirrers and may comprise rotating or swinging devices, such as an auger or paddle mechanism. Generally, conventional agitators rotate within the feed hopper. However, it is considered that this does not provide an adequately uniform feeding rate for the fuel into the combustion zone. Furthermore, the presence of the conventional agitator inside the feed hopper may serve to promote bridging within the feed hopper. This occurs when, for example, the conventional agitator has an axle or securing points which am down the centre of the feed hopper and which can act as a staging point for bridging and can in some cases double the likelihood that bridging will occur.

It would be desirable, therefore, to provide an agitator which does not incorporate any form of stirrer or similar appendage which may promote bridging within the feeding hopper..

SUMMARY OF THE INVENTION

Accordingly, a first aspect of the invention provides, an agitator comprising a hollow body for channelling solid material, and means for imparting agitative motion to the body. The motion imparting means may be arranged to impart reciprocating or vibratory- motion to the body of the agitator. The reciprocating or vibratory motion may be imparted to the body in a direction generally perpendicular to the direction in which said solid material is channelled through or by the body during use.

Alternatively, the motion imparting means may impart revolutional, or orbital, motion to the body of the agitator. The revolutional, or orbital, motion may be imparted to the body of the agitator in a plane generally perpendicular with the direction in which said solid material is channelled through or by the body during use.

In preferred embodiments, the motion imparting means is located externally of the agitator body. The agitator preferably includes means for coupling the agitator body to a feed hopper, the coupling means being arranged to allow relative movement between the body and the feed hopper. The coupling means may comprise means for suspending the agitator body from the feed hopper.

A second aspect of the invention provides a system comprising a feed hopper for containing solid material, the feed hopper comprising an outlet for the solid material, the system further comprising the agitator of the first aspect of the invention, the agitator being associated with the outlet of the feed hopper in order to receive solid material therefrom, and wherein the agitator is movable with respect to the feed hopper.

The system may comprise a gas producer wherein the feed hopper is arranged to feed solid material in the form of solid fuel into a combustion zone of the gas producer, the agitator being provided between the feed hopper and the combustion zone in order to channel said solid fuel from the feed hopper to the combustion zone. A third aspect of the invention provides a gas producer comprising the agitator of the first aspect of the invention. The agitator may be formed integrally with the agitator or may be formed separately, for example suspended from, the feed hopper.

Further advantageous aspects of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of a specific embodiment and with reference to the accompanying drawings.

As used herein, the term "feed hopper" is intended to embrace any component(s) of a system from or by which solid fuel, or other solid material, are fed from a first location towards and/or into a second location, and in particular towards and/or into the combustion zone, pyrolysis zone, drying zone, storage zone or feed zone of a gas producer or other system.

As used herein, the term "combustion zone" is intended to mean the region, also commonly known as the fuel bed, of a gas producer, or other system, in which fuel is combusted.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described by ^ay of example and with reference to the accompanying drawings, in which;

Figure 1 presents a schematic diagram of a downdraft gas producer incorporating an agitator embodying the present invention;

Figure 2 presents a perspective view of the agitator of Figure 1 ; Figures 3 to 5 illustrate respective alternative embodiments of the agitator;

Figure 6 illustrates an embodiment of a feed hopper which may be used in conjunction with an agitator embodying the invention; and Figure 7 illustrates an alternative embodiment of the feed hopper.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the accompanying drawings, there is Illustrated an agitator, generally indicated as 10, embodying the invention. As is described in more detail below, the agitator 10 channels solid material between two parts or components of a system. The solid material may be described as bulk solid material and comprises a quantity, or mass, of solid elements or pieces such as chips, chunks, lumps, shavings, pellets, powder, briquettes or other granular or particulate material. In some cases the solid material may be said to comprise flowable solid material. The agitator is particularly, but not exclusively, suitable for use with a gas producer, or gasifier 12, in which case the solid material may be said to comprise solid fuel. The gas producer 12 illustrated in Figure 1 is a downdraft gasifer, although agitators embodying the invention may alternatively be used with updraft gasifiers. It will be understood that the gas producer 12 represents one of a range of gas producers (not shown) which the agitator 10 may be adapted for use with. Moreover, it will be understood that the agitator 10 may be adapted for use with any other device or system in which solid material is channelled or fed from one location to another, and wherein bridging or similar blockages may occur. Examples of alternative applications would be in a pharmaceutical environment during the manufacture of tablets or the like, or in an agricultural environment in relation to particulate feed or aggregates.

The gas producer 12 comprises an outer casing 18 within which is provided a feed hopper 20. The feed hopper 20 divides the casing 18 into a first region or chamber 21 and a second region in the form of a combustion zone 22. The combustion zone 22 is located beneath the feed hopper 20. In use, solid fuel (not shown) of the general type hereinbefore described, is fed into the feed hopper 20 from the chamber 21. The fuel may be fed in a continuous, semi-continuos, batch or semi-batch manner. The solid fuel, which comprises solid material, moves or flows, typically under the influence of gravity, downwardly through the feed hopper 20 (in the direction of arrow A in Figure 1) and enters the combustion zone 22, whereupon the fuel is- converted into gas and waste by-products (not shown). The chamber 21 may be described as a storage chamber or bin for containing a feedstock of solid fuel.

The gas producer 12 includes a gas exhaust 24 through which the gas (not shown) produced within the gas producer 12 is extracted in the direction of arrow B. The gas may he stored, although it may alternatively be utilised directly from the gas producer 12. The gas producer 12 also incorporates one or more air inlets 26 (only one shown in Figure 1) which channel air, or alternatively pure oxygen directly into the combustion zone 22 (as indicated by arrow C) in order to elevate the temperature within the combustion zone 22 so as to increase the rate of combustion. The location of the air inlets 26 and the method of distributing the air/oxygen for combustion with the fuel will vary according to the type of gas producer 12.

The agitator 10 is incorporated into the gas producer 12 in association with means for imparting movement to the agitator 10. In the preferred embodiment, the agitator 10 is generally sleeve-like in form and the movement imparting means comprises an actuator in the form of a drive mechanism 14 and a coupling 16 provided between the agitator 10 and the drive mechanism 14. The agitator 10 is associated with, or coupled to, the feed hopper 20, intermediate the feed hopper 20 and the combustion zone 22, such that the outlet of the hopper 20 and the inlet, or mouth 13, of the agitator are at least partially in register with one another. As illustrated in Figure 1, it is preferred that the mouth 13 of the agitator 10 at least covers, and is preferably larger than, the outlet of the feed hopper 20 and, advantageously, the agitator 10 overlaps with the feed hopper 20 in the direction of flow (A). The solid fuel thus passes through the agitator 10 prior to reaching the combustion zone 22.

Figures 2 to 5 each show, by way of example, a respective alternative embodiment of the agitator 10. Each agitator 10 comprises a body 11 defining an inlet, or mouth 13 and an outlet 15 between which is defined a channel. Preferably, the body 11 is generally sleeve-like, or hollow. It will be understood that the shape and configuration of the agitator 10 may be altered or adapted in any way to suit the particular configuration of gas producer, or other system, in respect of which it is to be used. It the illustrated embodiments, the body 11 is generally cylindrical although this need not necessarily be the case. In some embodiments, the body 11 includes a funnel-shaped portion (see for example Figures 2, 3 and 4)..

The agitator 10 is moveable relative to the feed hopper 20 and the combustion zone 22. In the preferred embodiment, the agitator 10 is suspended^' from the feed hopper 20 by any suitable means, for example chains (not shown), although any other suitable means of connection may be to used to facilitate the required movement. The agitator 10 may alternatively or additionally be connected directly or indirectly to the outer casing 18, or be supported by any other means permitting relative movement between the agitator 10 and the feed hopper 20 and the combustion zone 22. The agitator 10 may alternatively be formed integrally with the feed hopper 20, with minor modifications peπmtting equivalent operation thereof.

Figures 6 and 7 each show a respective embodiment of the feed hopper 20. The feed hopper 20 may be formed integrally with, or separately from, the outer casing 18. The feed hopper 20 may be formed integrally with, or separately from, the storage chamber 21. In the preferred embodiment, the drive mechanism 14 is located externally of the outer casing 18 in order to avoid heat damage thereto. The drive mechanism 14 may alternatively be located internally of the outer casing 18 , although preferably out of the path of the fuel, in order to discourage bridging of the fuel. In the illustrated embodiment, the coupling 16 passes through the outer casing 18 and is connected to the exterior of the agitator 10. The coupling 16 may be of any suitable conventional configuration arranged to translate motion, for example, rotary motion, of the drive mechanism 14 into reciprocating, vibratory, revolutional or oscillatory motion, which is transmitted to the agitator 10. In one embodiment, generally linear reciprocating motion is imparted to the agitator 10, either continuously or intermittently, in a direction generally perpendicular to the direction of flow of the solid fuel (as indicated by arrow A in Figure 1). Alternatively, or in addition, the imparted movement may be in a direction generally parallel with arrow A and/or comprise generally revolutional or orbital movement around an axis generally parallel with the direction of arrow A. In any event, corresponding motion is imparted to the fuel located within the agitator 10. This motion has the effect of agitating, or mixing, the fuel in order to prevent the occurrence of bridging.

In preferred embodiments, the drive mechanism 14 and coupling 16, or other motion imparting means, are located externally of the body 11 of the agitator 10 and are arranged to act on an external part of the body 11 in order to move the body 11 as a whole. Hence, the solid fuel may be continually or intermittently agitated as it-passes through the agitator 10 without the need for any form of mechanical mixer being located within the agitator 10.

The drive mechanism 14 and the coupling 16 may be replaced by any other suitable means or mechanism for imparting a reciprocating, vibratory, oscillatory, revolutional, orbital or otherwise agitative motion to the agitator 10. For example, any suitable mechanical or electro-mechanical actuating mechanism such as a vibration motor, one or more linear or rotary actuators, a hydraulic/pneumatic assembly including one or more rams (not shown) or an electromagnetic assembly (not shown) would be suitable for this purpose.

The present invention is not limited to the embodiment described herein, which may be amended or modified without departing from the scope of the present invention.

Claims

CLAIMS:

1. An agitator comprising a hollow body for channelling solid material, and means for imparting agitative motion to the body.

2. An agitator as claimed in Claim 1 , wherein the motion imparting means is arranged to impart reciprocating or vibratory motion to the body of the agitator.

3. An agitator as claimed in Claim 2, wherein the motion imparting means is airanged to impart reciprocating or vibratory motion to the body in a direction generally perpendicular to the direction in which said solid material is channelled by the body during use.

4. A agitator as- claimed in Claim 1, wherein the motion imparting means is arranged to impart revolutional motion to the body of the agitator.

5. A agitator as claimed in Claim 4, wherein the motion imparting means is arranged to impart revolutional motion to the body of the agitator in a plane generally perpendicular with the direction in which said solid material is channelled by the body during use .

6. An agitator as claimed in any preceding claim, in which the motion imparting means is located externally of the agitator body.

7. An agitator as claimed in any preceding claim, wherein the agitator includes means for coupling the agitator body to a feed hopper, the coupling means being arranged to allow relative movement between the body and the feed hopper.

8. An agitator as claimed in Claim 7, wherein the coupling means comprises means for suspending the agitator body from the feed hopper.

9. An agitator as claimed in any preceding claim, wherein the body is generally sleeve-like.

10. An agitator as claimed in any preceding claim, wherein the motion imparting means is located externally of the body and is arranged to act on an external part of the body.

11. A system comprising a feed hopper for containing solid material, the feed hopper comprising an' outlet for the solid material, the system further comprising an agitator as claimed in Claim 1 , the agitator being associated with the outlet of the feed hopper in order to receive solid material therefrom, and wherein the agitator is movable with respect to the feed hopper.

12. A system as claimed in Claim 11, wherein the system comprises a gas producer.

13. A system as claimed in Claim 12, wherein the feed hopper is arranged to feed solid material in the form of solid fuel into a combustion zone of the gas producer, the agitator being provide between the feed hopper and the combustion zone in order to channel said solid fuel from the feed hopper to the combustion zone.

14. A gas producer comprising an agitator as claimed in Claim 1.