GB2277699A

GB2277699A - System for the treatment noxious fumes and fines entrained in a gas stream

Info

Publication number: GB2277699A
Application number: GB9309479A
Authority: GB
Inventors: Ivor Allen
Original assignee: FOUNDRY FUME TECHNOLOGY LIMITE
Current assignee: FOUNDRY FUME TECHNOLOGY LIMITE
Priority date: 1993-05-07
Filing date: 1993-05-07
Publication date: 1994-11-09
Anticipated expiration: 2013-05-07
Also published as: GB9309479D0; GB2277699B

Abstract

A system for the treatment of noxious fumes and fines entrained in a gaseous stream comprises a collection device (13, 14) which opens at the source (11, 12) of noxious fumes and fines and into which the noxious fumes and fines are drawn, a combustion means (18) for the combustion of noxious fumes and a filtering device (17) for the removal of fines from the gaseous stream, and ducting (15, 15a, 15b, 15c) extending from the collection device (13, 14) to the filtering device (17) and there being means (16) to create a gas stream within the ducting (15, 15a, 15b, 15c) and thus to draw the noxious fumes and fines into the collection device (13, 14) through the combustion means (18) and hence to the filtering device (17). <IMAGE>

Description

Title: System for the treatment of noxious fumes and fines entrained in a gaseous stream.

Description of Invention This invention relates to a system for the treatment of noxious fumes and fines entrained in a gaseous stream, and more particularly, but not exclusively, to such a system for use in treating noxious fumes such as volatile organic compounds and fines produced by the melting of scrap metal for example.

However the invention has much wider application.

New regulations on the emissions of toxic and harmful substances require the treatment of emissions which may be produced by foundries, in melting down of scrap metal, so as to incinerate noxious fumes and remove any fines which may be toxic, present in the emissions.

According to one aspect of the invention we provide a system for the treatment of noxious fumes and fines entrained in a gaseous stream comprising a collection device which opens at the source of the noxious fumes and fines and into which the noxious fumes and fines are drawn, a combustion means for the combustion of the noxious fumes, a filtering device for the removal of fines from the gaseous stream, ducting extending from the collection device to the filtering device and there being means to create the gaseous stream within the ducting and thus to draw the noxious fumes and fines into the collection device, through the combustion means and into the filtering device.

The invention thus provides for the virtually complete and efficient combustion of noxious fumes and for the removal of fines from the gaseous stream. By providing the combustion means "in line" such that the gaseous stream passes through the combustion means as it flows from the collection device to the filtering device, the fumes can be treated efficiently, so as not substantially to affect the gaseous flow in the system and in energy consumption terms.

According to a second aspect of the invention we provide a collection device for collecting noxious fumes and fines, the device comprising a hood movable from a first position in which the hood is close to the source of noxious fumes and fines, and a second position in which the hood is spaced from the source of fumes and fines, characterised in that the hood is movable generally vertically between the first and second positions.

As the hood is movable vertically, the hood is able to collect noxious fumes and fines when in both the first and second positions.

According to a third aspect of the invention we provide a combustion means for the combustion of noxious fumes present in a gaseous stream, the combustion means comprising a burner adapted to project a flame into the gaseous stream.

According to a fourth aspect of the invention we provide a filter device for removing fines from a gaseous stream, comprising a generally sealed first chamber into which the gaseous stream passes, there being a plurality of filter elements within the chamber depending generally vertically into the chamber and each being of a generally tubular configuration with a tube wall made of a filtering material and an internal hollow, with the lowermost end of each filter element being closed, and the hollow at an upper end of each filter element opening into a second chamber, the gaseous stream, in use, passing from the first chamber, through the walls of at least some of the filter elements into the internal hollows thereof, and hence into the second chamber, fines being removed from the gaseous stream by the filtering material of the tube walls.

The invention will now be described with reference to the accompanying drawings in which: FIGURE 1 is a schematic illustration of a system for the treatment of noxious fumes and fines in accordance with the first aspect of the invention.

FIGURE 2 is an enlarged view of the combustion means of the system of figure 1.

FIGURE 3 is a plan view of a filtering device of the system of figure 1.

FIGURE 3a is an enlarged side view of part of the filtering device of figure 3.

Referring to the drawings, there is shown a system 10 for the treatment of noxious fumes and fines produced in this example, by the melting of metal 11 in a crucible 12, for example during a scrap reclamation process. The crucible 12 may be heated for example by an induction heater, or by direct heat from an oil or gas burner for examples. It will be appreciated that scrap metal can contain many toxic or otherwise harmful incidental substances and contaminates which may be given off as the metal is melted.

Accordingly, there is provided a collection device comprising a hood 13 which is movable between the position shown in full lines in figure 1 immediately adjacent the crucible 12, in which the crucible 12 is substantially covered and virtually all fumes and fines produced by the melting metal can pass into the hood 13, and the position shown in dotted lines in figure 1 which is spaced above the crucible 12, sufficiently to permit the charging and discharging of the crucible 12. When the hood 13 is in the dotted line position, the hood 13 can still be operative to collect fumes and fines, although of course less efficiently than when the hood 13 is in its full line position.

Conventionally, hoods are movable out of an operating position to permit a crucible to be charged and discharged, by pivoting about a generally vertical axis. Hence during charging and discharging of the crucible, such hoods are not operative to collect any fumes or fines, as they are not located above the crucible 12.

According to an aspect of the invention the hood 13 is movable generally vertically between the full line and dotted line positions. In this example, the hood 13 includes an integral tube 14 which extends upwardly telescopically into a part 15a of ducting 15. Generally vertical movement of the hood 13 may be achieved manually for example using a counterweight mechanism and/or a pulley aided system or the like, but if desired, any powered means such as an electrical or other motive unit and an appropriate transmission, could be used if desired.

The hood 13 and ducting 15 are preferably each made of a corrosion resistant and/or heat resistant material such as stainless steel.

A gaseous stream is created in the ducting 15 by means of a fan 16 located downstream of a filtering device 17 of the system, so that the fumes and fines are drawn into the hood 13 by suction, and pass along the ducting 15 through a combustion means 18 and hence into the filtering device 17.

The fan 16 is preferably a dual speed fan at least, such that when the hood 13 of the collection device is in the dotted line position when it is spaced above the crucible 12, the amount of suction exerted by fan 16, and hence the gaseous stream within the ducting 15, can be increased, such that there is a greater suction at the hood 13. When the hood 13 is in its full line operative position as shown in figure 1, the fan 16 may be operated at its lower speed.

Where the heat for the crucible 12 is obtained from a gas or oil burner which itself produces noxious fumes, these fumes may be collected by any known means and fed into a chimney 15b which connects with the ducting 15 so that these noxious fumes too pass through the combustion means 18 and filtering device 17.

The combustion means 18 is shown in more detail in figure 2 and comprises a layer of insulation 19 being for example, ceramic fibre, within a length 15c of the ducting 15, the insulation 19 being held in position by means of a cylinder of expanded metal indicated at 20.

Within a hollow 22 of the expanded metal cylinder 20, there is provided a turbulating device 21 which causes turbulation of the gases of the gaseous stream, and the noxious fumes and fines entrained therein.

The device 21 comprises a spiral of sheet metal made for example of nickel chrome alloy or a similar material which can conveniently be made from rings of sheet material, cut and distorted, and then secured together. The device 21 is held in a central position of the hollow 22 by means of connecting struts 23 welded at appropriate points to the cylinder 20 of expanded metal. By virtue of this construction, there is a flow path for the gaseous stream both through the centre of the turbulating device 21, and around the turbulating device 21 between the device 21 and the cylinder 20 of expanded metal.

The combustion means 18 further comprises a branch of ducting 24 which is connected in an opening 25 through the length of ducting 15g, the opening 25 also extending through the insulation 19 and the cylinder 20 of expanded metal.

The branch 24 contains a burner 26 of the oil or gas type, which in use projects a flame F along the branch 24 and into the hollow 22 of the cylinder 20 of expanded metal. The burner 26 has an air supply provided by a fan 27 such that the flame F is projected into the hollow 22 rather than simply being drawn into the hollow 22 by the gaseous stream.

It has been found that the flame F tends to be drawn along the turbulating device 21 and due to the turbulance of the gas stream, there is a rapid rise in temperature and any noxious fumes present in the gaseous stream are efficiently incinerated. The burner 26 thus needs to have only a relatively small capacity. By using a simple low capacity oil or gas burner, temperatures of 1200"C and above have been achieved in a prototype combustion means 18. Typically the temperature of the gaseous stream which passes along the ducting 15 to the combustion means 18 is in the range of 475"C to 600"cm Using the particular construction described in which there is a passage for gaseous flow around the outside of the turbulating device 21, it has been found that there are no substantial deposits of fines etc. within the combustion device 18. Rather, the combustion device 18 would appear to provide no significant obstacle to flow therethrough of the gaseous stream and fines entrained therein.

The gaseous stream and fines entrained therein, passes from the combustion device 18 along further ducting 15, to the filtering device 17.

In this arrangement, the filtering device 17 comprises a chamber 30 having an upper part 31 and a lower part 32. The upper part 31 is in this example generally rectangular in side and plan section and has depending within it, a plurality (in this example 180) filter elements 33 each of which comprises a tube of ceramic filtering material comprising a tube wall 34 and an internal hollow 35.

The lower ends of each of the depending filter elements 33, are closed as indicated at 36 in figure 3a whilst the upper ends of the hollows 35 are open.

The filter elements 33 are all mounted in sealing engagement with a top chamber wall 37 and the hollows 35 thereof into a second chamber 38.

The ducting 15 containing the gaseous stream and fines entrained therein, opens into the lower part 32 of the chamber 30 and the gaseous stream is caused to flow upwardly into the upper part 31 of the chamber, through the walls 34 of at least some of the filter elements 33 and into the second chamber 38 above the first chamber 30.

Further ducting 39 connects the second chamber 38 and the fan 16 thus to draw the gases from the second chamber 38 to the fan 16, and hence into a chimney 40 for example, from where the resultant gaseous stream can be emitted.

The filter elements 33 of the filtering device 17, are arranged in nine rows of twenty such filter elements 33 in this example. Each row, for example row R1 indicated in figure 3, has an associated air feed pipe indicated at 42. Each air pipe 42 includes a plurality of feed pipes 43 each of which opens into a respective filter element 33. Each such pipe 42, for each of the nine rows R1-R9, extends from the second chamber 38 to a storage tank 44 of compressed air, there being a compressor 45 to charge the tank 44 at least to a predetermined pressure.

Each air feed pipe 42 of each row R1-R9 has an associated valve V1 V9, each of which is electrically operated by a controller means 50. The controller 50 is arranged to open the valves V1-V9 in sequence, such that at any time, one of the valves V1-V9 only, is open such that compressed air can flow from the tank 44 along the respective pipe 42 to the filter elements 33 of the respective row R1 R9.

The effect of this is as follows.

The fan 16 operates continuously such that the gaseous stream is continuously created within the ducting 15 and so that the gaseous stream and fines entrained therein are continuously drawn into the chamber 30.

Those rows R1-R9 of filter elements 33, for example rows R2-R9, whose respective valves V2-V9 are closed, will be effective to filter fines from the gaseous stream passing through the respective tube walls 34 of the filter elements 33. Hence the gaseous stream will continue to flow into the second chamber 38.

However, the compressed air being fed along the respective feed pipe 42 into the filter elements 33 of row R1, is of a sufficient pressure to negate the effect of suction within the hollows 35 of the tubes, and actually provides a positive pressure differential between the hollows 35 and the chamber 30.

Thus at least some of the fines which previously have been removed from the gaseous stream and are adhered to the filtering material of the walls 35 of the filter elements 33 of row R1, will become detached from the respective filter elements 33, and fall into the lower part 32 of the chamber, from whence they pass into a collection device 48 being for example a drum or the like, which is in sealing engagement with the chamber 30.

After a predetermined period, for example of a few seconds only, the valve V1 for the row R1 of filter elements 33, will be closed by the controller 50 and valve V2 for example, will temporarily be opened. Hence at least some of the fines adhering to the filter elements 33 of row R2 will be deposited into the drum 48, and so on for each of the rows R1-R9.

The controller 50 may always ensure that one of the valves V1-V9 is open at any time, or may be arranged only to open a respective valve V1-V9 in a predetermined sequence, at predetermined intervals.

Various modifications may be made without departing from the scope of the invention.

For example, if desired, the internal diameter of the ducting part 15c at which the combustion means 18 is provided, may be enlarged, such that the layer of insulation 19 and cylinder 20 of expanded metal, do not reduce the diameter of the ducting 15 at that point.

Although the turbulating device 21 described has been found to operate particularly efficiently and effectively, an alternative turbulating device 21 could be provided if desired.

Whereas it is preferred for the flame F produced by the burner 26 positively to be projected into the gaseous stream by providing a forced air supply by fan 27, if desired, the flame F could in an alternative design, simply be induced into the gaseous stream.

The filtering device 17 described, is only an example of a filter device which may be used in accordance with the invention.

An alternative filter device having any number of filter elements 33 to the one hundred and eighty shown in the drawing, may alternatively be provided.

These need not be arranged in a rectangular configuration in rows as described, but could be provided in an alternative configuration if desired.

The means which are provided for creating a positive pressure differential between the hollows 35 of the filter elements 32 and the chamber 30 in which they depend, may be provided by any alternative means to the air feed tubes 42/43 described. However the arrangement described has been found to work particularly effectively because the air tubes 42 and feed tubes 43 do not significantly restrict the gaseus flow into the second chamber 38, whilst filtering.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A system for the treatment of noxious fumes and fines entrained in a gaseous stream comprising a collection device which opens at the source of the noxious fumes and fines and into which the noxious fumes and fines are drawn, a combustion means for the combustion of the noxious fumes, and a filtering device for the removal of fines from the gaseous stream, ducting extending from the collection device to the filtering device and there being means to create the gaseous stream within the ducting and thus to draw the noxious fumes and fines into the collection device, through the combustion means and to the filtering device.

2. A system according to claim 1 in which the collection device comprises a hood movable from a first position in which the hood is close to the source of noxious fumes and fines and a second position in which the hood is spaced from the source of fumes and fines characterised in that the hood is movable generally vertically between the first and second positions.

3. A system according to claim 2 wherein the hood has integrally provided therewith or secured thereto a tube which extends generally vertically upwardly and is in use received telescopically within an opening of the ducting.

4. A system according to claim 3 wherein means are provided for raising and lowering the hood without disengaging the tube from the ducting.

5. A system according to any one of claims 2 to 4 wherein mechanically assisted means are provided for raising and lowering the hood, comprising a counterweight mechanism and/or pulley aided system.

6. A system according to any one of claims 2 to 4 wherein power operated means are provided for raising and lowering the hood comprising an electrical or other motive means and an appropriate transmission.

7. A system according to any one of claims 1 to 6 wherein the combustion means comprises a burner adapted to project a flame into the gaseous stream.

8. A system according to claim 7 wherein the ducting comprises a branch, and the burner is located within said branch.

9. A system according to any one of claims 1 to 8 wherein the combustion means comprises a turbulating device to cause turbulation of the gaseous stream and noxious fumes and fines entrained in it, the burner being adapted to project the flame into the turbulating gaseous stream.

10. A system according to claim 9 wherein the turbulating device comprises a spiral of sheet metal which is located centrally of the gaseous flow such that there is a flow path both through the turbulating device, and around the turbulating device.

11. A system according to any one of claims 7 to 10 wherein the combustion means comprises a length of ducting, a lining of insulating material within the length of ducting and means for retaining the lining.

12. A system according to claim 11 wherein the turbulating device is connected to the means which retain the lining of insulating material in position, by means of connecting struts which do not substantially affect flow through the length of ducting.

13. A system according to any one of the preceding claims wherein the filtering device comprises a generally sealed first chamber into which the gaseous stream passes, there being a plurality of filter elements within the chamber depending generally vertically within the chamber and each being of a generally tubular configuration with a tube wall made of a filtering material and an internal hollow, with the lowermost end of each filter element being closed and the hollow at an upper end of each filter element opening into a second chamber, the gaseous streams in use, passing from the first chamber through the walls of at least some of the filter elements into the internal hollows thereof and hence into the second chamber, fines being removed from the gaseous stream by the filtering material of the tube walls.

14. A system according to claim 13 wherein the sealed chamber of the filtering device comprises an upper part in which the plurality of filter elements depend, and a lower part into which the gaseous stream passes from the ducting.

15. A system according to claim 14 wherein the second chamber is located generally vertically above the first mentioned chamber, there being further ducting connecting the second chamber to a fan which is operative to draw the gaseous stream from the collection device along the ducting into the filtering device, through the filter elements and into the second chamber.

16. A system according to any one of claims 13 to 15 wherein means are provided to create within each of the filter elements, a positive pressure differential between the hollow of the filter element and the sealed chamber, against the direction of gaseous flow.

17. A system according to claim 16 wherein the means for providing a positive pressure differential comprises compressed air fed from a source of compressed air under the control a controller.

18. A system according to claim 17 wherein the filter elements are arranged in groups,-each group of filter elements having an associated valve controlled by the controller, the valve for each group of filter elements being controlled such that when opened, compressed air flows to each of the filter elements of the group to create the positive pressure differential between the hollows of the filter elements and the sealed chamber.

19. A system according to claim 18 wherein the valves of the groups of filter elements are operated in a sequence such that the filter elements which have a positive pressure created in them relative to the pressure within the sealed chamber, changes sequentially.

20. A system according to claim 19 wherein the source of compressed air comprises a tank of air under pressure, and a compressor.

21. A system for the treatment of noxious fumes and fines according to any one of the preceding claims wherein the source of noxious fumes and fines is melting metal.

22. A system for the treatment of noxious fumes and fines substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

23. A collection device for collecting noxious fumes and fines comprising a hood movable from a first position in which the hood is close to the source of noxious fumes and fines and a second position in which the hood is spaced from the source of fumes and fines, characterised in that the hood is movable generally vertically between the first and second positions.

24. A collection device for collecting noxious fumes and fines substantially as hereinbefore described with reference to and as shown in figure 1 of the accompanying drawings.

25. A combustion means for the combustion of noxious fumes and fines present in a gaseous stream comprising a burner adapted to project a flame into the gaseous stream.

26. A combustion means for the combustion of noxious fumes present in a gaseous stream substantially as hereinbefore described with reference to and as shown in figures 1 and 2 of the accompanying drawings.

27. A filtering device for removing fines from a gaseous stream comprising a generally sealed first chamber into which the gaseous stream passes, there being a plurality of filter elements within the chamber depending generally vertically within the chamber and each being of a generally tubular configuration with a tube wall made of a filtering material, and an internal hollow, with the lowermost end of each filter element being closed, and the hollow at an upper end of each filter element opening into a second chamber, the gaseous stream in use passing from the first chamber, through the walls of at least some of the filter elements into the internal hollows thereof, and hence into the second chamber, fines being removed from the gaseous stream by the filtering material of the tube walls.

28. A filtering device for removing fines from a gaseous stream substantially as hereinbefore described with reference to and as shown in figures 1, 3 and 3a of the accompanying drawings.

29. Any novel feature or novel combination of features as herein defined and/or shown in the accompanying drawings.