AU3946700A - Fumigation apparatus - Google Patents

Description

WO 00/62607 PCT/AUO0/00336 Fumigation Apparatus Field of the Invention The present invention relates generally to a 5 fumigation apparatus. The invention will primarily be described with reference to its use to provide fumigation of timber dunnage and other waste shipping cargo packaging material, but it should be realised that the invention can have broader applications to any other bulk materials, LO goods or produce which may contain pests or insects or other vermin and which therefore require fumigation. Background to the Invention Large quantities of timber and packing materials are carried all over the world in ships and such goods remain L5 largely useless at the point of arrival of the ship due to the likelihood of it containing pests, parasites, insects or other vermin from another country, such as for example borers, lice, ticks, fleas or termites. It is best that the timber dunnage and other bulk materials do not have to 20 leave the confines of the wharf or port vicinity to travel to a distant site for effective treatment, since this would pose an environmental exposure risk. Fumigation devices for bulk materials are known in the art that involve placement of a heavy, impervious blanket 25 or other covering article over the materials followed by subsequent addition of toxic gas flow under the blanket to fumigate the covered goods. Current methods of fumigation under blankets are crude, ineffective at fully eliminating insect infestation since no mixing of gases with dunnage 30 can occur, and highly dangerous from an occupational health standpoint since the gases used for effective fumigation are extremely toxic. US patent No. 5,318,789 relates generally to a method for fumigating produce and in particular fruit. US 35 5,318,789 describes the specific construction of a vented container in which the fruit is packed in preparation for WO 00/62607 PCT/AU00/00336 -2 fumigation. The vented fruit containers are stacked in a purpose-built fumigation chamber of a fumigation facility and the fruit fumigated with a gaseous fumigant. The fruit containers are then transported out of the fumigation 5 facility either to a cold storage area of a packing house or directly to shipment vehicles. Summary of the Invention According to one aspect of the present invention there is provided a fumigation apparatus comprising: 10 a conventional shipping container which at least in part defines a fumigation chamber being adapted to contain produce to be fumigated; fumigant inlet means operatively coupled to the container to allow a flow of a fumigant into the fumigation 15 chamber; and extraction means also being operatively coupled to the container to remove a majority of the fumigant from the fumigation chamber. Preferably the fumigation apparatus further comprises 20 control means operatively coupled to the shipping container and arranged to control the flow of fumigant into said container. Typically the fumigation apparatus also comprises another conventional shipping container positioned 25 alongside the shipping container and providing a control room in which the control means is located. Alternatively the fumigation apparatus further comprises a partition wall dividing the shipping container into the fumigation chamber and a control room in which the control means is located. 30 Preferably the partition wall and/or the shipping container itself is secure against the passage of the fumigant. This means that toxic gases from the process in the fumigation chamber will not pose any occupational health risk to operators of the fumigation apparatus during 35 processing, while they may be standing in the control room. It also provides an all weather secure location for WO 00/62607 PCT/AUOO/00336 -3 associated control equipment. Preferably the fumigation apparatus further comprises absorption means operatively coupled to the extraction means, said absorption means being designed to absorb at 5 least part of the fumigant extracted from the fumigation chamber. More preferably said absorption means comprises an absorption bed including activated carbon to which at least part of the extracted fumigant attaches. Typically the fumigation apparatus also comprises a 10 sliding bed or floor on which the produce resides, said bed or floor being configured to slide into and out of the fumigation chamber wherein loading and unloading of the produce to be fumigated can be performed externally of said chamber. 15 Preferably the control room incorporates a source of the fumigant which is preferably directly associated with a heating source, the latter used to convert the fumigant into a gaseous form. The heat energy transferred to the fumigant should be such that it becomes more buoyant than 20 ambient air. In another variant the fumigation apparatus has a source of the fumigant and a heating source which are contained in an appropriate storage box which is secure against the passage of gases. Alternatively the fumigant inlet means is adapted to detachably couple to a mobile 25 source of the fumigant such as a motor vehicle on which a fumigant vessel is mounted. Preferably the control room incorporates a system control box and a system of fumigant delivery pipes and valves adapted in use to supply fumigant from the supply 30 source to the fumigation chamber. Preferably the fumigation chamber has openable doors in the container, the end doors when closed being secure against the passage of fumigant and further being fitted with external locking cam devices adapted to be secured 35 with a latch and pin arrangement. More preferably the sliding bed or floor of the fumigation apparatus WO 00/62607 PCT/AUOO/00336 -4 facilitates loading and removal of produce for fumigation via the end doors. Preferably the fumigant inlet means includes a dispersion pipe system located in the upper part of the 5 fumigation chamber. Such an arrangement allows the fumigant, which is generally heavier than air, to fall in a dispersed fashion downward over the top of the produce such as the timber and dunnage charge which has been loaded into the fumigation chamber. 10 Preferably the fumigation chamber is provided with a plurality of mixing fans adapted to circulate fumigant and gases within the chamber. Such an arrangement allows more even and thorough dispersion of the fumigant and gases as they enter and are dispersed in the fumigation chamber. 15 Preferably the extraction means includes a pipe attached to an orifice located in a lower region of a partition or a container wall, the pipe being connected in turn to an actuated butterfly valve further connected in turn to a contra-rotating fan adapted to provide suction 20 for the extraction of the fumigant. More preferably the extraction means includes an exhaust stack positioned vertically above the fumigation container, the uppermost terminal of the exhaust stack being fitted with a gas diffuser and appropriate rain guard, and the exhaust stack 25 being arranged to receive the stripped fumigant stream. Preferably the fumigation chamber contains a plurality of small diameter floor and wall-mounted pipes independently connected via an appropriate system of taps and connectors to a fumigant sampling and detection meter 30 unit located in the control room. More preferably the floor and wall-mounted pipes may be further adapted to be located in recessed grooves which may form part of the construction of the walls or floor of the container. Preferably the control room includes a system control 35 box which contains the fumigant sampling and detection meter unit and power supply switches for mixing fans, WO 00/62607 PCT/AUOO/00336 -5 exhaust fan, lights, gas heaters and valve actuators. In the preferred embodiment of the invention the fumigation apparatus is constructed within a conventional shipping container. Such a container is in all respects 5 suitable for handling and use in the wharf or port vicinity. In fact, if available, effective fumigation of dunnage on site at the wharf by skilled operators would allow for the safe treatment and removal of this material for re-use as firewood or for building purposes, would 10 eliminate the possibility of insects or vermin escaping into the environment, would speed up the fumigation processing rate and would provide some enhanced health and safety benefits. According to another aspect of the invention there is 15 provided a method of fumigating produce, said method comprising the steps of: providing a fumigation apparatus including a conventional shipping container which at least in part defines a fumigation chamber; 20 locating the produce to be fumigated in the fumigation chamber; providing a flow of a fumigant to the fumigation chamber; and extracting at least some of the fumigation from said 25 chamber. Preferably the method of fumigating produce also comprises the step of absorbing at least part of the fumigant extracted from the fumigation chamber. More preferably said fumigant extracted from the chamber is 30 absorbed on an absorption bed. Typically the method of fumigating produce further comprises washing at least part of the absorption bed to remove the absorbed fumigant. More typically the absorption bed is washed with a scrubbing solution, such as 35 sodium thiosulphate, to yield one or more salts, such as bromide and sodium methylthiosulphate.

WO 00/62607 PCT/AU0O/00336 -6 Generally the fumigant includes an alkyl halide such as methyl bromide. The produce is usually timber. Brief Description of the Drawings Notwithstanding any other forms which may fall within 5 its scope, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a perspective schematic view of a shipping container fitted internally in accordance with one 10 embodiment of the invention with a fumigation chamber and a control room; Figure 2 is a similar view to Figure 1 showing the flow direction of gas between process units; and Figure 3 is a perspective schematic view of another 15 embodiment of the fumigation apparatus. Detailed Description of the Preferred Embodiments As shown in Figures 1 and 2 there is one embodiment of a fumigation apparatus comprising a conventional shipping container 10, a partition wall 14 dividing the container 10 20 into a control room 12 and a fumigation chamber 16. The control room 12 contains a heating source 18 and a source of a liquified fumigation reagent 20 both items contained in a storage box 22 secure against the passage of gases. The control room also has a vented door 23 to provide 25 external access. Piping means 24 exist for the supply and distribution of heated fumigant or in this example toxic gases directly to the fumigation chamber 16. Such an arrangement ensures firstly that the heavy toxic gas molecules, for example methyl bromide, are appropriately 30 gasified and dispersed in air for transfer into the fumigation chamber 16. The gas-tight storage box 22 ensures that the toxic gases being fed to the fumigation process will not pose any occupational health risk to operators of the fumigation apparatus while those operators 35 may be standing in the control room 12 during that period when the gas undergoes heating during processing.

WO 00/62607 PCT/AU00/00336 -7 The control room 12 contains a system control box 26 which functions to control the flow of toxic gas into the fumigation chamber 16. Such an arrangement ensures that at all times the availability of fumigation gases is able to 5 be manually controlled which ensures that highly safe operating procedures can be maintained. A nominal number of mixing fans, in this case two fans 28 and 30, circulate gases within the fumigation chamber 16 when operating. Mixing fans such as 28 and 30 located by 10 appropriate wall-mountings on the partition wall 14 dividing the container 10 into a fumigation chamber 16 and a control room 12 would provide sufficient circulation to prevent the toxic gases, which are heavier than air, from only locating in the lower portion of the fumigation 15 chamber 16. Gas-tight end doors 32 provide access to the fumigation chamber 16 when it is not operating. A sliding bed or floor 34 is included in the container 10 to slide in and out of gas-tight end doors 32. Such an arrangement 20 means that bulk quantities of large individual or odd shaped pieces of timber and dunnage may be conveniently loaded into the fumigation chamber 16 because of the size of the doors 32 and the access provided by the sliding bed or floor 34. Conventional shipping containers such as 10 25 have gas-tight end doors 32 which makes them very suitable pieces of equipment in this regard. Extraction means for evacuation of the fumigation chamber gases includes a pipe 36 attached to an orifice 38 located in the lower region of the partition 14, the pipe 30 36 in turn connected to an actuated butterfly valve 40 and a contra-rotating fan 42 and thence to a pipe exhaust stack 44. The uppermost terminal of the stack 44 is fitted with a gas diffuser and appropriate rain guard 46. Control of the actuated butterfly valve 40 and contra-rotating fan 42 35 are by means of system control box 26. Such an arrangement allows the toxic, heavier than air gases to be removed by WO 00/62607 PCT/AUOO/00336 -8 fan induced suction from the fumigation chamber 16 at an appropriate lower height, where said gas molecules will naturally congregate without recirculation, followed by dispersion to the external atmosphere via a stack 44 which 5 is of sufficient height to allow the gas contents of the fumigation chamber 16 to be safely vented without occupational health risk exposure to operators or others located nearby the fumigation apparatus. A plurality of gas sampling lines 48 are mounted on 10 both the walls and floor of the fumigation chamber 16 and connected via an appropriate system of pipes and connectors to a gas flow meter test unit located within system control box 26. Such an arrangement provides a gas sampling system which is connected in use to a gas flow meter test unit 15 which draws small amounts of the gaseous contents of the fumigation chamber 16 and delivers a reading as to the concentration of toxic gas remaining in the fumigation chamber 16 during the venting procedure. This monitoring is carried out to ensure that the main fumigation chamber 20 doors 32 may be safely opened for the purposes of removing the charged timber and dunnage material without occupational health risk exposure to operators or others located nearby the fumigation apparatus. System control box 26 also includes power supply 25 switches and circuits for operating heating source 18, mixing fans 28 and 30 and, as stated earlier, actuated butterfly valve 40 and contra-rotating fan 42. Interior lights 50 would also be controlled from the system control box 26. Such an arrangement provides a central and 30 securable location for all electrically operated devices, which is important when sequential operational steps are required. During use, dunnage and timber material for fumigation is loaded onto the sliding floor 34 and then inserted into 35 the fumigation chamber 16 using gas-tight end doors 32 to provide access for the load. The end doors 32 are then WO 00/62607 PCT/AUOO/00336 -9 sealed and heated toxic gases, generated by warming liquified fumigation reagent 20 by means of heating source 18, directly enter the fumigation chamber 16 via piping means 24. System control box 26 functions to control the 5 flow of toxic gas into the fumigation chamber. As best illustrated in Figure 2, the mixing fans 28 and 30 circulate gases within the fumigation chamber 16 when in use to provide good mixing of toxic gases with the charged material. When the fumigation interval is complete, the 10 recirculation fans 28 and 30 are switched off, the flow of toxic gas into the chamber 16 is stopped and gas is evacuated from the fumigation chamber 16, flowing consecutively through orifice 38, pipe 36, actuated butterfly valve 40 and contra-rotating fan 42 before 15 exiting the apparatus via pipe exhaust stack 44. As a safety check of the concentration of toxic gases remaining in the fumigation chamber 16, gas samples are drawn via a plurality of the gas sampling lines 48 to a gas flow meter test unit located within system control box 26 and a 20 readout is obtained so that the operator may ascertain when it is safe to reopen end doors 32 and remove the dunnage and timber material from the sliding floor 34 after fumigation. At this point the apparatus is ready for a new load of material for fumigation and a repeat procedure. 25 Figure 3 depicts another embodiment of the fumigation apparatus including a pair of conventional forty (40) foot shipping containers 100A and 100B located alongside one another. In this particular construction of the invention the control room 120 is formed from a twenty (20) foot 30 shipping container 130 located alongside adjacent ends of the forty (40) foot shipping containers 10OA/B. In order to avoid repetition and for ease of reference similar components and features of this alternative embodiment of the invention has been designated with an additional "0", 35 such as the control room 120. In this other embodiment of Figure 3 the fumigation WO 00/62607 PCT/AU0O/00336 -10 apparatus includes absorption means in the form of an absorption bed such as 150 located downstream of the valve 400. The absorption bed 150 includes activated carbon to which the fumigant, in this example methyl bromide, 5 attaches or is absorbed and is thus stripped from the gas/fumigant extracted from the fumigation chamber such as 160. Otherwise the extraction means is similar in construction to the preceding example of the fumigation apparatus. 10 The control room 120 of the twenty (20) foot container 130 is provided with the heating source or heat exchanger 180 and the source of fumigant, in this embodiment liquified methyl bromide. The piping means (not shown) which is located in a ceiling of each of the fumigation 15 chambers such as 160 is operatively coupled to the heating source 180 and liquified fumigation reagent source 200. The methyl bromide attaches to the activated carbon of the absorption bed 150 prior to discharge of the fumigant/gas mixture from the fumigation apparatus. The 20 absorption bed 150 is periodically washed with a scrubbing solution, such as sodium thiosulphate. In this embodiment scrubbing of the absorption bed 150 with sodium thiosulphate yields bromide and sodium methylthiosulphate which are non-toxic salts which can be discharged safely to 25 the environment. Thus, the methyl bromide gas is degraded following its fumigation and then extraction from the fumigation apparatus. Now that several preferred embodiments of the present invention have been described in some detail it would be 30 apparent to those skilled in the art that the fumigation apparatus has at least the following advantages over the admitted prior art; 1. The fumigation apparatus is adapted from a conventional shipping container and thus is relatively 35 convenient and uncomplicated to fabricate; 2. The fumigation apparatus is relatively effective WO 00/62607 PCT/AU00/00336 -11 in fumigating produce; and 3. The fumigation apparatus is "environmentally friendly" in its fumigation and discharge of the fumigant. Those skilled in the art will appreciate that the 5 invention described herein is susceptible to variations and modifications other than those specifically described. For example, the source of fumigant need not be located in the fumigation apparatus but rather may be mounted on a mobile vehicle such as a utility truck. The invention need not be 10 restricted to methyl bromide as the fumigant but rather extends to any substance which is suitable in fumigating produce and thus killing pests, parasites, insects, or vermin. The invention need not be restricted to the specific constructional features described and may for 15 example not include the sliding bed or floor. All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description. 20

Claims (22)

1. A fumigation apparatus comprising: a conventional shipping container which at least in 5 part defines a fumigation chamber being adapted to contain produce to be fumigated; fumigant inlet means operatively coupled to the container to allow a flow of a fumigant into the fumigation chamber; and 10 extraction means also being operatively coupled to the container to remove a majority of the fumigant from the fumigation chamber.

2. A fumigation apparatus as defined in claim 1 further 15 comprising control means operatively coupled to the shipping container and arranged to control the flow of fumigant into said container.

3. A fumigation apparatus as defined in claim 1 or 2 also 20 comprising another conventional shipping container positioned alongside the shipping container and providing a control room in which the control means is located.

4. A fumigation apparatus as defined in claim 1 or 2 25 further comprising a partition wall dividing the shipping container into the fumigation chamber and a control room in which the control means is located.

5. A fumigation apparatus as defined in any one of the 30 preceding claims further comprising absorption means operatively coupled to the extraction means, said absorption means being designed to absorb at least part of the fumigant extracted from the fumigation chamber. 35

6. A fumigation apparatus as defined in claim 5 wherein said absorption means comprises an absorption bed including WO 00/62607 PCT/AUOO/00336 -13 activated carbon to which at least part of the extracted fumigant attaches.

7. A fumigation apparatus as defined in any one of the 5 preceding claims also comprises a sliding bed or floor on which the produce resides, said bed or floor being configured to slide into and out of the fumigation chamber wherein loading and unloading of the produce to be fumigated can be performed externally of said chamber. 10

8. A fumigation apparatus as defined in any one of the preceding claims wherein the control room incorporates a source of the fumigant which is directly associated with a heating source, the latter used to convert the fumigant 15 into a gaseous form.

9. A fumigation apparatus as defined in any one of claims 1 to 7 wherein the fumigant inlet means is adapted to detachably couple to a mobile source of the fumigant. 20

10. A fumigation apparatus as defined in claim 3 or 4 wherein the control room incorporates a system control box and a system of fumigant delivery pipes and valves adapted in use to supply fumigant from a supply source to the 25 fumigation chamber.

11. A fumigation apparatus as defined in claim 7 wherein the fumigation chamber has openable doors in the container, the end doors when closed being secure against the passage 30 of fumigant and further being fitted with external locking cam devices adapted to be secured with a latch and pin arrangement.

12. A fumigation apparatus as defined in claim 11 wherein 35 the sliding bed or floor of the fumigation apparatus facilitates loading and removal of produce for fumigation WO 00/62607 PCT/AUO0/00336 -14 via the end doors.

13. A fumigation apparatus as defined in any one of the preceding claims wherein the fumigant inlet means includes 5 a dispersion pipe system located in the upper part of the fumigation chamber.

14. A fumigation apparatus as defined in any one of the preceding claims wherein the fumigation chamber is provided 10 with a plurality of mixing fans adapted to circulate fumigant and gases within the chamber.

15. A fumigation apparatus as defined in any one of the preceding claims wherein the extraction means includes a 15 pipe attached to an orifice located in a lower region of a partition or a container wall, the pipe being connected in turn to an actuated butterfly valve further connected in turn to a contra-rotating fan adapted to provide suction for the extraction of the fumigant. 20

16. A fumigation apparatus as defined in claim 16 wherein the extraction means includes an exhaust stack positioned vertically above the fumigation container, the uppermost terminal of the exhaust stack being fitted with a gas 25 diffuser and appropriate rain guard, and the exhaust stack being arranged to receive the stripped fumigant stream.

17. A fumigation apparatus as defined in any one of the preceding claims wherein the fumigation chamber contains a 30 plurality of small diameter floor and wall-mounted pipes independently connected via an appropriate system of taps and connectors to a fumigant sampling and detection meter unit located in the control room. 35

18. A fumigation apparatus as defined in claim 3 or 4 wherein the control room includes a system control box WO 00/62607 PCT/AUOO/00336 -15 which contains a fumigant sampling and detection meter unit and power supply switches for mixing fans, exhaust fan, lights, gas heaters and valve actuators. 5

19. A method of fumigating produce, said method comprising the steps of: providing a fumigation apparatus including a conventional shipping container which at least in part defines a fumigation chamber; 10 locating the produce to be fumigated in the fumigation chamber; providing a flow of a fumigant to the fumigation chamber; and extracting at least some of the fumigation from said 15 chamber.

20. A method of fumigating produce as defined in claim 18 also comprising the step of absorbing at least part of the fumigant extracted from the fumigation chamber. 20

21. A method of fumigating produce as defined in claim 19 wherein said fumigant extracted from the chamber is absorbed on an absorption bed. 25

22. A method of fumigating produce as defined in claim 19 or 20 further comprising washing at least part of the absorption bed to remove the absorbed fumigant. 30