WO2013008000A2

WO2013008000A2 - Feed compactor variable orifice outlet

Info

Publication number: WO2013008000A2
Application number: PCT/GB2012/051618
Authority: WO
Inventors: Scott Edmondson; Bruce Toase
Original assignee: NEW EARTH ADVANCED THERMAL TECHNOLOGIES Ltd
Current assignee: NEW EARTH ADVANCED THERMAL TECHNOLOGIES Ltd
Priority date: 2011-07-12
Filing date: 2012-07-09
Publication date: 2013-01-17
Anticipated expiration: 2014-01-12
Also published as: GB201111917D0; WO2013008000A3; GB2492790A; GB2492790B

Abstract

A feed compactor outlet (2) comprising a passage wall defining a passage adapted to discharge material from a feed compactor to a reactor (12), wherein the passage wall comprises a moveable portion (4), the moveable portion (4) being moveable with respect to a longitudinal axis of the feed compactor outlet (2) to vary a throat area of the passage.

Description

FEED COMPACTOR VARIABLE ORIFICE OUTLET

The present disclosure relates to a feed compactor outlet and particularly but not exclusively relates to a feed compactor outlet for a pyrolysis reactor.

Background

Pyrolysis and gasification are processes which have been used in commercial energy applications for over 100 years, most notably the gasification of coke in steam engines. More recently pyrolysis and gasification have been used in waste material applications.

Pyrolysis is a thermo-chemical decomposition of organic material into char and occurs in the absence of oxygen and at elevated temperatures. By contrast, gasification converts organic materials into a number of gases including carbon monoxide, hydrogen, carbon dioxide and methane. Gasification is a process which occurs in the presence of a controlled amount of oxygen and/or steam and occurs at elevated temperatures.

The chemical science in waste applications is identical to the gasification of coke in steam engines. However, in the case of pyrolysis, the waste material is first converted into char that may then be gasified. In either case, hydrocarbons are liberated from the source fuel (char or coke) in the same way and these hydrocarbons may then be used to generate energy, for example in the form of electricity and/or heat. The pyrolysis and then gasification process (at approximately 600°C) convert the heterogeneous waste into a homogenous high temperature gas fuel (referred to as syngas) which is then immediately oxidised (burnt) at very high temperature (approximately 1250°C).

The combustion in either case is very complete and as such minimises the formation of pollutants such as carbon monoxide (CO), volatile organic compounds (VOCs), dioxins and particulates. Unlike conventional incineration, gas from the waste is burned, not the waste itself. Energy may then be reclaimed using a high-pressure steam boiler and turbine, or using scrubbers and a gas engine. The exhaust gases can be put through further abatement processes to ensure optimal environmental performance.

In a previously-proposed power generating waste process a feed compactor may feed a reactor with compacted waste feed material. The reactor may use pyrolysis and/or gasification and the feed compactor may use one or more auger screws to force the waste into the reactor. In addition to the feed compactor comprising an auger screw, a pyrolysis reactor may be in the form of a tube containing an auger screw. In this case, the compressed waste itself may provide an atmospheric plug-type seal at the inlet of the auger screw to ensure that air does not affect the pyrolysis reaction.

The compaction ratio and resulting density of the waste material provided by the feed compactor will affect the seal quality. The compaction ratio and material density are, for a given feed material, typically determined by the geometry of the feed compactor auger and associated outlet. If the feed material composition changes, the density of the waste material provided by the feed compactor, which acts as a plug at the inlet of the pyrolysis auger, will also change and this can lead to unwanted air leakage through the material plug seal. This may adversely affect the pyrolysis or gasification reaction which ideally occurs in the absence of air or in a controlled quantity of oxygen respectively.

The present disclosure therefore seeks to address this issue. Statements of Invention

According to a first aspect of the present invention there is provided a feed compactor outlet comprising a passage wall defining a passage adapted to discharge material from a feed compactor to a reactor, wherein the passage wall comprises a moveable portion, the moveable portion being moveable with respect to a longitudinal axis of the feed compactor outlet to vary a throat area of the passage.

The moveable portion may be an elongate portion, e.g. a finger. The passage wall may comprise a plurality of the moveable portions. The moveable portions may be disposed about an opening of the feed compactor outlet. The moveable portions may be substantially equiangularly spaced about the opening.

The moveable portions may be tapered along their length. For example, a narrow end of the tapered moveable portions may define the variable throat area of the passage. The moveable portions extend in a direction of the longitudinal axis of the feed compactor outlet. For example, the moveable portions may extend in a direction having axial and radial components only. Alternatively, the moveable portions may extend in a direction having also a tangential or circumferential component.

Each moveable portion may pivot with respect to the opening of the feed compactor outlet. A pivot axis of each moveable portion may extend in a direction tangential to the opening of the feed compactor outlet. Alternatively, the pivot axis of each moveable portion may extend in a direction angled with respect to a direction tangential to the opening of the feed compactor outlet. The pivot action of the moveable portion with respect to the opening of the feed compactor outlet may comprise rotation about a point or alternatively flexing or bending with respect to the opening of the feed compactor outlet.

The or each moveable portion may be moved with an actuator. The actuator may be a hydraulically, pneumatically or electrically activated. The actuator may be manually and/or automatically adjustable, e.g. with a control system.

A variable restrictor may encircle the moveable portions. The variable restrictor may be operable to adjust the position of at least an end of the moveable portions relative to the longitudinal axis of the feed compactor outlet. The variable restrictor may encircle the moveable portions at or towards a narrow end of the tapered moveable portions. The variable restrictor may be manually and/or automatically adjustable.

The variable restrictor may comprise an elongate element which is arranged such that upon tightening of the elongate element, the moveable portions are deflected toward the longitudinal axis. The elongate element may comprise a chain, band, cord, cable or any other elongate tensioning element. Accordingly, one or more ends of the elongate element may be moveable to tension the elongate element. For example one end of the elongate element may be fixed, e.g. with respect to the feed compactor outlet, whilst the opposite end may be free to move. Alternatively, both ends of the elongate element may be moveable, e.g. with respect to each other. In either case a first end of the elongate element may pass through an aperture formed at a second end of the elongate element. By way of example, the elongate element may be in the form of a jubilee clip or any other device adapted to provide a radial force. The feed compactor outlet may comprise one or more friction reducing elements which may be disposed between the moveable portions and the variable restrictor, e.g. the elongate element, such that the elongate element runs over the friction reducing elements. The friction reducing elements may comprise one or more of pulleys, rollers, ball bearings, lubrication, a low friction material layer or any other friction reducing element. The friction reducing elements may reduce the capstan effect between the moveable portions and the elongate element.

The reactor may be a pyrolysis reactor or gasification reactor or any other reactor, which may produce heat and/or gas from a feed material. The pyrolysis reactor may comprise an auger screw. The feed compactor may comprise an auger screw. The feed compactor may be inclined relative to the reactor. The auger screw of the feed compactor may be inclined relative to the pyrolysis auger screw.

According to a second aspect of the present invention there is provided a method of discharging material from a feed compactor outlet to a reactor, the feed compactor outlet comprising a passage wall defining a passage adapted to discharge material from a feed compactor to the reactor, wherein the method comprises: moving one or more movable portions of the discharge wall with respect to a longitudinal axis of the feed compactor outlet to vary a throat area of the passage. The present invention advantageously reduces air ingress into the reactor: By varying the throat area of the feed compactor outlet, the compaction ratio and hence density of the feed material going into the reactor can be controlled. For example, reducing the throat area will increase the compaction ratio and density of the feed material. A denser feed material, particularly in the case of a pyrolysis reactor, ensures that the feed material itself may form a good seal with the walls of the compactor outlet so that air ingress into the reactor is minimised and the pyrolysis reaction is improved. Furthermore, the denser feed material may prevent material burn back in the feed system, which may lead to a plant shutdown. The variable throat area of the feed compactor outlet may also allow for the use of different feed materials. For example, by varying the throat area the compaction ratio may be changed for different feed materials. This may ensure that the density of the feed material entering the reactor is approximately constant regardless of the feed material used. As a result the same reactor may be used for different feed materials and the reactor will not have to be changed depending on the feed material, thereby saving time and money. Equally, multiple reactors for different feed materials may not be required and one or more common reactors need only be provided thanks to the variable throat of the feed compactor outlet.

Brief Description of the Drawings

For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a perspective view of a feed compactor outlet according to an embodiment of the invention; and

Figure 2 is a cross-sectional view of the feed compactor outlet coupled to a reactor. Detailed Description

With reference to Figure 1 , a feed compactor outlet 2 according to an embodiment of the invention is shown. The feed compactor outlet 2 comprises a plurality of fingers 4 which are spaced around an outlet of an auger screw 6. The auger screw 6 forms part of a feed compactor. The fingers 4 extend from the outlet of the auger screw 6 in a direction of a longitudinal axis of the feed compactor outlet 2 (i.e. the direction of the fingers 4 has axial and radial components only).

The fingers 4 are movably connected to the outlet of the auger screw 6 so that they can pivot with respect to the longitudinal axis of the feed compactor outlet 2 about the point of connection (e.g. they are movable in a radial direction). For example, the fingers 4 may be connected to the outlet of the auger screw 6 by a pivot pin type fastener. Alternatively, the fingers 4 may be pivoted by flexing or bending the fingers 4. The pivot axis of the fingers 4 may extend in a tangential direction or may be angled with respect to the tangential direction to allow the fingers 4 to overlap one another. The feed compactor outlet 2 may comprise a flange, such as an annular ring, which is disposed adjacent to the outlet of the auger screw 6, and the fingers 4 may be movably connected to the flange. In the illustrated embodiment, the fingers 4 are substantially triangular and taper from a relatively wide end at the connection with the outlet of the auger screw 6 to a relatively narrow distal end. The fingers 4 are coupled to one another by a variable restrictor 8. The variable restrictor 8 is an elongate element, such as a band, which is curved to form a tensioning ring that has a variable diameter. For example, the variable restrictor may use a jubilee clip type arrangement. The variable restrictor 8 encircles the fingers 4 at their distal ends. Friction reducing elements may be provided to reduce the friction between the variable restrictor 8 and the fingers 4 as the diameter is varied. For example, the friction reducing elements may comprise one or more of pulleys, rollers, ball bearings, lubrication, a low friction material layer or any other friction reducing element.

The fingers 4 define a passage through the feed compactor outlet 2 and the variable restrictor 8 defines a throat area of the passage (i.e. the smallest diameter of the passage). The throat area of the passage may be varied by adjusting the diameter of the variable restrictor 8 and thus moving the fingers 4 with respect to the longitudinal axis of the feed compactor outlet 2. The tapering profile of the fingers 4 allows the throat area to be reduced without adjacent fingers 4 interfering with one another.

As shown in Figure 2, the feed compactor outlet 2 is encased within a tubular member 10 which seals the feed compactor outlet 2 from the outside atmosphere and connects the feed compactor to a reactor 12, such as a pyrolysis or gasification reactor. The tubular member 10 allows the throat area to be varied whilst maintaining the sealing between the feed compactor and the reactor 12. The reactor 12 may comprise an auger screw for conveying the material through the reactor 12. As shown, the feed compactor may be inclined relative to the reactor 12. The incline may allow any expressed liquor in the feed compactor outlet 2 to be drained at the rear of the feed compactor. Furthermore, this arrangement may assist in part-filling the flights of the auger screw 6, thereby reducing sheer torque at the inlet to the feed compactor outlet 2. In use, the auger screw 6 is driven by a variable speed drive. The rotation of the auger screw conveys material through the feed compactor and to the feed compactor outlet 2 where it is forced through the passage defined by the fingers 4. The pitch of the auger screw 6 reduces along the length of the feed compactor so as to compact the material as it progresses through the feed compactor. Furthermore, the variable restrictor 8 is set so that the feed compactor outlet 2 tapers to the throat area defined by the variable restrictor 8. Consequently, the material is compacted as it is forced through the feed compactor outlet 2, thereby further increasing the density of the material. The material therefore provides a plug seal at the throat area of the feed compactor outlet 2. The plug seal prevents the ingress of air into the reactor 12. The density of the material which exits the feed compactor outlet 2 is related to the density of the material which enters the feed compactor. Accordingly, variations in the density of the material entering the feed compactor have an effect on the quality of the plug seal. The compaction ratio (i.e. the ratio of the volume of material entering the feed compactor to the volume of material exiting the feed compactor outlet 2) can be controlled by varying the diameter of the throat area. As described previously, the diameter of the throat area may be adjusted using the variable restrictor 8 to move the fingers 4 toward or away from the longitudinal axis of the feed compactor outlet 2. With this mechanism, the feed compactor outlet 2 is able to mitigate against variations in the density of the material entering the feed compactor and thus maintains a substantially constant density at the exit of the feed compactor outlet 2.

Specifically, if the material entering the feed compactor has a lower initial density such that a higher compaction ratio is required, the diameter of the throat area is reduced. This increases the back pressure in the feed compactor and therefore increases the compaction ratio to maintain the desired plug density.

Likewise, if the material entering the feed compactor has a higher initial density such that a lower compaction ratio is required, the diameter of the throat area is increased. This decreases the back pressure in the feed compactor and therefore decreases the compaction ratio to maintain the desired plug density.

The material is able to expand after it leaves the feed compactor outlet 2 and enters the reactor 12. However, the material forming the plug seal at the throat area of the feed compactor outlet 2 is constantly replaced to provide a continuously sealed system.

The variable restrictor 8 may be adjusted to set the throat area during commissioning of the system with regard to the type of material which is to be used in the process. Alternatively, or in addition, a feedback loop may be used to ensure the optimum compaction ratio is maintained at all times. Such a feedback loop may be particularly useful where varying materials are used in the system. The torque applied by the auger screw 6 is measured and may be used as an indication of the density of material at the throat area. In particular, the torque will increase as the density increases since a greater force will be required to force the material through the feed compactor outlet. This measurement can be used in the feedback loop for adjusting the variable restrictor 8. That said, alternative indications of the density may be used which will be apparent to a person skilled in the art. An actuator such as a motor or hydraulic/pneumatic actuator may be used to adjust the variable restrictor 8 in response to the density indications. The adjustment of the variable restrictor 8 may be carried out automatically or with input from an operative.

Although the invention has been described as using a variable restrictor which encircles the distal ends of the fingers, each finger may instead be moved using an actuator, such as a hydraulically, pneumatically or electrically activated actuator. The actuator may be manually and/or automatically adjustable, e.g. with a control system. Furthermore, the variable restrictor 8 need not encircle the distal ends of the fingers 4 and may instead be located towards the other end of the fingers.

Other types of feed compactor may be used instead of the auger-type compactor described herein, so long as the compactor is able to force the material through the feed compactor outlet. For example, a ram compactor may be used.

Although the feed compactor outlet and auger screw have been described as discrete elements, they may be integrally formed.

As a result of the triangular shape of the fingers 4, gaps are formed between adjacent fingers 4. As described previously, the gaps allow the throat area to be reduced without adjacent fingers 4 interfering with one another. The gaps may be left open, as shown in Figure 1 . Alternatively, to prevent material from passing through the gaps, they may be covered. For example, adjacent fingers 4 may be joined by a flexible membrane which is connected to opposing edges of the adjacent fingers 4. The flexible membrane prevents material from passing through the gaps whilst allowing the throat area to be reduced. As described previously, the pivot axis of the fingers 4 may be angled with respect to the tangential direction to allow the fingers 4 to overlap one another. With this arrangement, it may not be necessary for the fingers 4 to taper and thus the gaps between adjacent fingers 4 can be removed.

Alternatively, first and second sets of fingers 4 may be provided. Each set of fingers 4 may be spaced around the outlet of the auger screw 6, with the pivot axis of the fingers 4 extending in a tangential direction. The first set of fingers 4 may be disposed within the second set of fingers 4. In other words, the fingers 4 of the first set are tangential to a smaller circle than the fingers 4 of the second set. Gaps are disposed between adjacent fingers 4 of each set so as to allow the throat area to be reduced. The first and second sets of fingers 4 are offset from one another so that the fingers 4 of one set cover the gaps between adjacent fingers 4 of the other set. This arrangement prevents material from passing through the gaps whilst allowing the throat area to be reduced.

In another embodiment (not shown), the passage of the feed compactor outlet may be formed by a duct having a rectangular cross-section. In this embodiment, one or more walls of the duct are movable relative to the other walls so as to vary the cross- sectional area of the duct. The movable walls may be pivotable so as to taper the cross-sectional area of the duct. Where all of the walls are movable they may converge to form a duct having a frusto-pyramidal shape.

Claims

1 . A feed compactor outlet comprising a passage wall defining a passage adapted to discharge material from a feed compactor to a reactor, wherein the passage wall comprises a moveable portion, the moveable portion being moveable with respect to a longitudinal axis of the feed compactor outlet to vary a throat area of the passage, wherein the passage wall comprises a plurality of the moveable portions, the moveable portions being about an opening of the feed compactor outlet, and wherein a variable restrictor encircles the moveable portions and is operable to adjust the position of at least an end of the moveable portions relative to the longitudinal axis of the feed compactor outlet.

2. The feed compactor outlet of claim 1 , wherein the moveable portions are tapered along their length with a narrow end of the tapered moveable portions defining the variable throat area of the passage.

3. The feed compactor outlet of claim 1 or 2, wherein the moveable portions extend in a direction of the longitudinal axis of the feed compactor outlet.

4. The feed compactor outlet of any preceding claim, wherein the moveable portions extend in a direction having a tangential or circumferential component.

5. The feed compactor outlet of any of claims 1 to 4, wherein each moveable portion pivots with respect to the opening of the feed compactor outlet.

6. The feed compactor outlet of claim 5, wherein a pivot axis of each moveable portion extends in a direction tangential to the opening of the feed compactor outlet.

7. The feed compactor outlet of claim 5, wherein a pivot axis of each moveable portion extends in a direction angled with respect to a direction tangential to the opening of the feed compactor outlet.

8. The feed compactor outlet of claim 1 to 7, when dependent on claim 3, wherein the variable restrictor encircles the moveable portions at or towards a narrow end of the tapered moveable portions.

9. The feed compactor outlet of claim 8, wherein the variable restrictor comprises an elongate element which is arranged such that upon tightening of the elongate element, the moveable portions are deflected toward the longitudinal axis.

10. The feed compactor outlet of any of claims 8 or 9, wherein one or more ends of the elongate element are moveable to tension the elongate element.

1 1 . The feed compactor outlet of any of claims 1 to 10, wherein the feed compactor outlet comprises one or more friction reducing elements disposed between the moveable portions and the elongate element such that the elongate element runs over the friction reducing elements.

12. The feed compactor outlet of any of claims 1 to 1 1 , wherein the variable restrictor is manually and/or automatically adjustable.

13. A method of discharging material from a feed compactor outlet to a reactor, the feed compactor outlet comprising a passage wall defining a passage adapted to discharge material from a feed compactor to the reactor, wherein the method comprises:

moving one or more movable portions of the discharge wall with respect to a longitudinal axis of the feed compactor outlet to vary a throat area of the passage.

14. A feed compactor outlet substantially as described herein, with reference to and as shown in the accompanying drawings.

15. A feed compactor comprising the feed compactor outlet of any preceding claim.

16. A feed compactor as claimed in claim 15, further comprising an auger screw for supplying the material to the feed compactor outlet.

17. A pyrolysis and/or gasification reactor comprising the feed compactor of claim 15 or 16.

18. A pyrolysis and/or gasification reactor as claimed in claim 17, wherein the feed compactor is inclined relative to the reactor.

19. A pyrolysis and/or gasification reactor as claimed in claim 18 when dependent on claim 16, wherein the reactor comprises an auger screw which is inclined relative to the auger screw of the feed compactor.

20. A method of discharging material from a feed compactor outlet substantially as described herein, with reference to and as shown in the accompanying drawings.