AU2017204228A1 - Gas removal system - Google Patents

Abstract

A gas exhaust and dispersion system addressing the need for flexibility between the a gas chamber 62 and a dispersion device 20, and delivering exhaust to a satisfactory height or distance from the dispersion device 20, including: a gas chamber 62, sealed 5 to the exterior environment 66; an exhaust device including: an inlet port 40a adapted to be connected to the gas chamber 62 through which chamber gas is extracted from the gas chamber 62; a relief port 40b adapted to be connected to the gas chamber 62 and spaced from the inlet port 40a; a relief port valve 52b to stop, slow or allow the flow of gas through the relief port 40b; a flexible duct 56 adapted to be connected to 0 the inlet port 40a; an axial fan 54 installed at any point along the flexible duct 56 and adapted to create a positive pressure in the flexible duct 56; and a flexible duct valve 52a installed at any point along the flexible duct 56 and adapted to stop, slow or allow the flow of gas through the flexible duct 56. )C CD co (0 o c-Q (00 cqN (0 (D CO Lo ((0 (.00

Description

GAS REMOVAL SYSTEM FIELD OF INVENTION

This invention relates to a gas removal and dispersion system. In particular, this invention relates to the removal and dispersion systems for removing fumigation gases.

BACKGROUND ART

The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

Gas extraction and dispersion systems have been described in which a fan system connected to a chimney stack sucks gas out of a sealed structure and ventilates the gas to the atmosphere via the chimney stack at a relatively low exit velocity. Generally, the fan system is located in or at the base of the chimneystack or between the sealed structure and the chimneystack. Solid non-flexible ductwork connects the sealed structure to the fan system and chimneystack or chimneystack containing a fan system. The nature of such extraction and dispersion systems is that they are fixed systems and not suitable for use on portable structures.

Fumigation chambers have been described as sealed structures used to contain commodities requiring fumigation, in which they are exposed to high concentrations of fumigant gases. Both portable and fixed structures are used for fumigation. Examples of fixed fumigation chambers include: sealed warehouses and grain silos. Portable fumigation chambers include shipping containers and ship holds. A fumigation chamber may also be formed by a tarpaulin securely positioned over items to be fumigated and sealed against the atmosphere by a weighted bead extending around a base at ground or floor level.

Dispersion of residual fumigant gases from portable fumigation chambers is typically effected by passive ventilation. Post fumigation, ship holds may be ventilated by opening the man-ways, cargo-hold ventilators or by opening the cargo hatches. Similarly tarpaulin fumigations may be ventilated by removing the weighted bead from the perimeter of the tarpaulin and then lifting the front and back of the tarpaulin to allow the residual fumigation gases to ventilate into the atmosphere.

The dispersion of residual fumigation gases as described above is highly dependent on prevailing wind and weather conditions. Poor dispersion conditions can create a serious occupational health and safety hazard for the operators and nearby workers. Fumigations are often conducted in industrialised or populated areas whereby passive release of residual fumigation gases post fumigation can represent a public health hazard.

Whilst this may disperse fumes over time by dilution and dispersion dependant on natural, surrounding conditions, in the case of toxic fumigant fumes it represents a serious occupational and health hazard for the operator and nearby workers. Such facilities are often in industrialised or populated areas whereby release of the fumes post-fumigation can represent a public health hazard, depending on wind direction at or near ground level where fume-containing gas is dispersed at ground level.

Active fumigation systems for toxic gases may include expensive and inefficient filtration equipment such as scrubbers. These systems extract toxic gas from the sealed structure and attempt to either capture the toxic gas on activated carbon or chemically react the toxic gas with a reagent. Hence, the use of the hazardous, passive ventilation methods described above.

Toxic gas exhaust and dispersion systems have been described in which a large high velocity fan located above ground level on a stand sucks gas from the areas below the fan and blows the gases upwardly high into the atmosphere.

It is understood that application of the high velocity dispersion fan used to disperse fumigation gases has not been done, wherein the ductwork leading into the high velocity dispersion fan needs to be adapted for manoeuvrability and portability.

STATEMENT OF INVENTION

According to the present invention in its broadest aspect, there is provided a gas-removal system adapted to remove gas from a gas chamber filled with the gas, including: dilution-dispersion-means adapted to displace the gas into atmosphere outside the gas chamber; removal-means adapted to connect the gas chamber to the dilution-dispersion-means to allow the gas in the gas chamber to be removed from the chamber via the removal-means to the dilution-dispersion-means, and displaced by the dilution-dispersion-means into the atmosphere; wherein the dilution-dispersion-means includes propulsion-means capable of displacing a substantial portion of the gas in an upwardly directed plume so that the gas is at least capable of being diluted high in the atmosphere.

Preferably: the removal-means includes an exhaust or extraction device; the dilution-dispersion-means includes a dilution and dispersion device; and the propulsion-means comprises a dispersion fan.

Preferably, the gas-removal system is in the form of a gas exhaust or extraction, and dilution and dispersion system.

The invention according to one or more particular aspects is as defined in the independent claims. Some optional and/or preferred features of the invention are defined in the dependent claims. The invention will be described with greater specificity below.

Accordingly, in a first particular aspect of the invention there is provided: A gas exhaust or extraction, and dilution and dispersion system including: an exhaust or extraction device including: an inlet port adapted to be connected to a gas chamber filled with gas to be extracted and to receive extracted chamber gas from the gas chamber; a flexible duct adapted to be connected to the inlet port; an extraction fan installed near or in the inlet port and adapted to create a positive pressure in the flexible duct; and a dilution and dispersion device including: a dispersion fan mounted on a support structure; an air inlet adapted to receive air from the environment surrounding the dispersion device whereby to dilute a stream of ex-chamber gas exiting the extraction device; a dilution and dispersion device inlet adapted to receive air from the output of the flexible duct; a dispersion fan inlet zone; a dispersion fan outlet; a control system adapted to control at least one device in the gas extraction, dilution and dispersion device; and a power supply system adapted to power at least one component included in the gas extraction, dilution and dispersion device; wherein: the dispersion fan inlet zone is adapted to be in fluid communication with the air inlet and the flexible duct outlet, such that the air inlet and the flexible duct outlet lead into the dispersion fan inlet zone; the dispersion fan is adapted to draw gas from the exterior environment and chamber gas from the flexible duct outlet whereby to form at the dispersion fan inlet zone a combined stream of diluted gas from the exterior environment and chamber gas from the flexible duct; the dispersion fan outlet is exposed to the exterior environment; the dispersion fan outlet is adapted to deliver the combined stream of diluted gas substantially upwardly; and the dispersion fan has a high velocity capacity, capable of displacing a substantial portion of the gas received by the dispersion fan inlet zone in an upwardly directed plume.

The gas chamber is advantageously sealed to the exterior environment. The gas chamber may have a relief port that is spaced from the location of the connection with the inlet port. The relief port may have a relief port valve. The relief port valve is preferably operable to stop, slow or allow the flow of gas through the relief port. The relief port may be significantly spaced from the inlet port and is preferably on the opposite side of the gas chamber to the inlet port.

The gas chamber may be a silo, a ship hold, a shipping container, a gas proof tarpaulin or a similar structure that may be used to contain materials, such as logs or other agricultural produce or building materials that may need to be fumigated.

For example, in the case of logs, the gas chamber maybe a tarpaulin made of woven or meshed and lined material, and/or polymeric sheeting material, that is resistant to gas leakage through the sheet material. The tarpaulin may be a single large sheet, or may comprise a plurality of sheets joined at common peripheral edges by welds, zip means, hook and loop attachment means, press studs or other means adapted to resist leakage at the joined edges.

Most preferably, the tarpaulin is described as gas proof and may be sealed around its perimeter by a tube filled with water. The perimeter bead may be adapted to compress the tarpaulin to make a seal by pressing the tarpaulin peripheral edge against a substrate, such as a hard stand, sealed ground surface, tarmac, etc. Where the tarpaulin is larger than necessary to cover the material to be fumigated, the peripheral edge is considered to be where the tarpaulin meets the substrate. In considering the meaning of the term “sealed”, the term includes a defined area that is either substantially, effectively or completely sealed. In considering the term “substantially sealed” it is understood by the skilled person that negligible exchange of fluid may occur between the sealed space within the gas chamber and the immediate environment. The immediate or exterior environment is typically the atmospheric air surrounding the gas chamber.

The inlet port may include a funnel, conically shaped, or tapering walled, channel.

The inlet port may have, near or at its wide mouth end for receiving extracted gas, a rectangular cross section that is adapted to be inserted into a hole, gap or a pocket in the gas chamber. The inlet port may include a funnel shaped pipe with converging side walls and substantially flat and substantially parallel upper and lower walls. Preferably, the inlet port includes a funnel shaped channel with a rectangular cross section. Sometimes referred to as a “whale tale” in the industry. The inlet port may include a bulkhead. Preferably, the inlet port includes an outer sealing device and a funnel shaped channel with a rectangular cross section and is detachably connected to the extraction fan.

In the case of the chamber being formed by a tarpaulin, when the material has been sufficiently fumigated, the inlet port may be placed between the substrate and an edge of the tarpaulin such that the sealing of the gas chamber is maintained. The channel is therefore preferably in fluid communication with the gas chamber, optionally interposed by an inlet port valve. This may allow gas extraction through the inlet port. The inlet port may be positioned between the tarpaulin and the substrate.

The inlet port may include an outer sealing device adapted to assist the existing seal the gas chamber makes with the inlet port. The inlet port may include baffles to provide structural or supporting ribs for the inlet port. The inlet port may be detachably connected to the extraction fan. Preferably, the inlet port allows gas exchange through the inlet port.

The chamber gas may include a target gas such as Methyl bromide, Phosphine, Ethandinitrile, Carbon dioxide or any other fumigation gases generally used for fumigating products. Preferably, the chamber gas is Methyl bromide.

The relief port may include the same features as the inlet port. The relief port may be spaced from the inlet port in that the relief port may be located on the opposing side or location to the inlet port such. The ports are preferably spaced a maximum distance from each other. Preferably, the relief port is located on the opposing side or location to the inlet port.

The relief port may have a valve. Preferably, the relief port valve includes a butterfly valve. The relief port may be manually or electronically actuated. Preferably, the relief port valve is manually actuated. The relief port valve may be electronically actuated using wireless signals, such as radio frequency signals or may be actuated by signals transmitted through wires to actuate the relief port valve.

The flexible duct may be a tube or other conduit for conveying gas or vapour. The flexible duct is flexible in that it is capable of bending easily without breaking. The flexible duct is preferably collapsible and/or foldable for easy transport and storage. The flexible duct may include a duct or any other conveyance providing a conduit to provide a passage for the extracted gas, wherein the duct is flexible. The flexible duct may include rigid components or features such as reinforcing rings. The reinforcing rings may comprise sprung plastic or metal ribs or coil. The flexible duct may have no rigid structures except for attachment devices. For example, the flexible duct may be an inflatable tube made of fabric or flexible plastic sheeting. The flexible duct may be rigid in the axial direction but flexible in bending. The flexible duct may include flexible corrugated pipe. The flexible duct may include rubber or plastic hose. Preferably, the flexible duct includes a flexible plastic sheeting type material and reinforcing rings. The flexible duct may comprise tarpaulin sheeting material folded lengthwise to join its long edges to form a seam. The flexible duct may include materials such as rubber, plastic and steel. The flexible duct may include a composite material. Preferably, the flexible duct is made of plastic. The flexible duct may lead into a filter before going into the dispersion device, the output air of the filter then leading into the dispersion device. The flexible duct may connect directly or indirectly into the dispersion device. Preferably, the flexible duct connects directly into the dispersion device.

The inlet port may include valve means. The inlet port valve may be a butterfly valve. Preferably, the inlet port valve may include a butterfly valve. The inlet port valve may be electronically actuated. Preferably, the inlet port valve is manually actuated. The inlet port valve may be electronically actuated using wireless signals or signals transmitted through wires to actuate the inlet port valve.

Both the extraction and the dispersion fans are devices for moving fluid by the rotation of their respective impellers and may be described as turbomachines. Preferably, the dispersion and extraction fans are axial fans for direct displacement of gas inline whereby their axes of rotation are parallel to the corresponding gas stream. However, either or both of the extraction and the dispersion fans may be offset from the gas stream or may have a rotational axis normal or transverse to the direction of travel of the corresponding gas stream.

The extraction fan may be a compressor. The extraction fan may be any type of powered fan. The extraction fan may include other turbomachinery capable of increasing the pressure of gas in a pipe, such as the flexible duct. Preferably, the extraction fan is an axial fan.

The extraction fan may include a pair of fans, including a priming fan and a duct fan. The pair of extraction fans may be located in the relief port and the inlet port, respectively. The extraction fan preferably creates a positive pressure along the length of the flexible duct. In this specification, “positive pressure” in this context refers to a pressure in the flexible duct which is higher than the negative pressure generated by the dispersion fan. Preferably, the positive pressure at the outlet of the extraction fan may be between approximately +21 Pa and +1200 Pa. Most preferably the positive pressure at the outlet of the extraction fan may be between +600 Pa and +900 Pa. In general terms the positive pressure at the outlet of the extraction fan is about +800 Pa. Preferably the negative pressure at the inlet of the dispersion fan is between -20 Pa and -1199 Pa. Most preferably the negative pressure at the inlet of the dispersion fan is between -100 Pa and -600 Pa. In general terms the negative pressure at the inlet of the dispersion fan is about -350 Pa.

Pressure measurements at the dispersion fan inlet are taken at a position immediately preceding the dispersion impeller, for example, within about 1 m of the upstream side of the impeller. Pressure measurements at the extraction fan outlet are taken at a position immediately following the extraction impeller, for example, within about lm of the downstream side of the impeller. The quantum of the negative pressure at the inlet of the dispersion fan will be less than the quantum of the positive pressure at the outlet of the extraction fan, for example, at least 1 Pa less, and preferably 400 - 500 Pa less.

In this specification, high velocity is intended to be interpreted to mean that the corresponding gas leaves the dispersion fan outlet at high speeds in a generally upwardly direction. The actual path and shape of the plume ultimately is determined by local climatic conditions, such as temperature, humidity, and wind speed and direction. For example, the gas velocity at the dispersion fan outlet may be of the order of 15m/s or greater. The velocity of the exiting gas is preferably of the order of about 15 to about 50m/s, preferably about 20 to about 40m/s, and most preferably about 25 to about 30 m/s, whereby, ideally in still conditions, the diluted gas is delivered upwardly into the atmosphere to a height of between about 50m to about 100m. In non-still conditions, the diluted gas may be at least partially blown laterally by natural wind forces whereby the ambient wind forces facilitate the dilution and dispersion of the target gas from the chamber site.

The dispersion fan may include an air moving device such as an impellor or a high powered fan. The dispersion fan may include an electric motor, which drives the air moving device. The dispersion fan may include a compressor which pumps air out of a nozzle at the dispersion fan inlet. The dispersion fan may include a fan housing which forms a circumference around or surrounds at least one portion the air moving device. Preferably, the dispersion fan includes an impellor, an electric motor and a fan housing. The dispersion fan may include one or more impellors. For example, the dispersion fan may include two or more impellers in parallel. The multiple impellors may be arranged in a manifold to unify the gas streams from the each of the impellers downstream.

The fan housing may include support beams or other components necessary to hold, the dispersion fan. The fan housing may include the control system and/or the power supply system. The fan housing may include a cylinder. The cylinder may include a tapered portion along the axial direction of the cylinder. For example, part of the cylinder may concentrically taper to form a section of a truncated cone. The cylinder may include a tapered portion which includes curved faces along the axial direction of the cylinder. Preferably, the fan housing includes support structures and the cylinder. Most preferably, the cylinder includes a tapered portion surrounding the outlet of the dispersion fan, such that the cylinder tapers down to its minimum circumference at the dispersion fan outlet.

The support structure may hold, cover and/or support components of the gas extraction and dispersion system and other components commonly used with the gas extraction, dilution and dispersion system. The support structure, which the dispersion fan is mounted to, may include supporting components such as brackets, beams and bolts. The support structure may include attachment points which may be used to lift, move or transport the dispersion device. The support structure may include slots, rings or holes which may be used to provide contact regions for forklift forks or other moving or lifting devices. The support structure may include panels to contain or cover parts of or all of the dispersion device. The support structure may cover and/or support at least a portion of the air inlet, the flexible duct gas outlet, the dispersion fan inlet zone, the dispersion fan outlet and/or the control and power supply system. The support structure may include holding devices for at least one component included in the extraction device. The holding devices may include a holding device for the flexible duct, such as a set of hooks to wrap the flexible duct around. The holding devices may include a holding device for the relief port valve, the flexible duct valve, the inlet port and/or the relief port. For example, the holding device may include hooks, tethers, straps and the like. The holding devices may include holding devices for other components which are commonly used with the gas extraction, dilution and dispersion system, such as a tarpaulin and water duct. The support structure may include wheels, an axel, a chassis and other necessary components for the support structure to function as a trailer. The support structure may include mounting holes or mounting points such that the support structure is mountable to a truck or transportation vehicle. Preferably, the support structure includes brackets, beams, bolts, attachment points, contact regions for forks, panels and holding devices.

The gas extraction and dispersion system may be portable or a fixed installation. The gas extraction and dispersion system may be permanently or temporarily secured to a structure such as a ship, silo or warehouse. Preferably, the gas extraction, dilution and dispersion system is portable. The gas extraction, dilution and dispersion system may be transported on a vehicle, such as a truck or utility vehicle tray or a vehicle trailer.

Advantageously therefore, the gas extraction, dilution and dispersion system or a significant portion of the components of the system may be transported as a trailer unit or on a trailer. The gas extraction, dilution and dispersion system may be transported on a truck. The gas extraction, dilution and dispersion system may be moved from the truck to the location in which it is being operated using a crane and/or forklift. The dispersion system may be operated while on a truck or trailer. Preferably, the gas extraction, dilution and dispersion system is transported on a truck and moved using a forklift to the location in which it is being operated.

The air or exterior inlet may lead directly into the dispersion fan inlet. The flexible duct outlet may lead into the dispersion fan inlet zone. The air or exterior inlet may include duct work, a cavity or pipe work to transport the air. The air or exterior inlet may include a mesh screen. The air or exterior inlet may include a filter. Preferably, the air or exterior inlet includes a mesh screen and duct work. The air or exterior inlet may receive air from the environment immediately adjacent the dispersion device. The air or exterior inlet may receive air from an area at a certain distance spaced from the dispersion device. For example, the air may be received by an external duct which takes in air from a region about 1 - 10m away from the dispersion device. The air or exterior inlet may correspond to the region under the dispersion fan, such that the exterior inlet forms part of the dispersion fan inlet zone. Preferably, the air or exterior inlet receives air from the area directly surrounding the dispersion device. A scrubber device may be interposed in the system such that the scrubber extracts chamber gas from the gas chamber and the extraction fan on the scrubber feeds the gas into the flexible duct and into the dispersion fan. Preferably the system extracts chamber gas directly from the gas chamber via the inlet port.

The environment surrounding the dispersion device refers to the atmospheric air around the dispersion device. This air may be taken from the environment near or adjacent to the dispersion device.

The flexible duct may lead into the dispersion fan outlet zone, such that chamber gas is fed into a high velocity stream of fresh air. Preferably, however, the flexible duct outlet may lead directly into the dispersion fan inlet zone. The flexible duct outlet may lead into the air or exterior inlet, which then leads into the dispersion inlet zone. The flexible duct outlet may be positioned under the dispersion fan inlet zone, such that the chamber gas is received together with the stream of atmospheric air being drawn into the dispersion fan inlet zone. Preferably, the flexible duct outlet leads directly into the dispersion fan inlet zone. The flexible duct outlet may include a duct, a cavity or pipe work that delivers the gas to the inlet zone. The flexible duct outlet may include a gas filter, such as a scrubber. Preferably, the flexible duct outlet includes a duct or adapter.

The dispersion fan inlet may include the portion of the fan housing below the dispersion fan. The dispersion fan inlet may include the region or area of gas below the dispersion fan which significantly contains the stream of gas drawn in by the dispersion fan. The dispersion fan inlet may include a cylinder or enclosed duct directly below the dispersion fan. The dispersion fan inlet may include the Y-junction tube, pipe or duct where the air or exterior inlet and the flexible duct outlet meet. Preferably, the dispersion fan inlet includes the cylinder or enclosed duct directly below the dispersion fan.

The dispersion fan outlet may include the portion of the fan housing above the dispersion fan. The dispersion fan outlet may include the region of gas above the dispersion fan which significantly contains the stream of gas exiting the dispersion fan. The dispersion fan outlet may include other ducts or pipes attached to the fan housing above the dispersion fan. The dispersion fan outlet and inlet may each include a mesh screen to prevent objects damaging or entering the dispersion fan housing and for safety reasons. The dispersion fan outlet may include channels, fins or guide vanes which direct and maintain the stream of gas coming out of the dispersion fan. Preferably, the dispersion fan outlet may include a portion of the fan housing downstream of the dispersion fan impeller. A mesh screen may be positioned above the impeller to protect the impeller from random debris, etc.

The control system may include a variable speed drive to control the motor powering the dispersion fan, a control panel to provide a user interface to operate all the electronics in the gas extraction, dilution and dispersion system, a computer system and electronic cables. The control system may also include sensors such as temperature, chemical composition, pressure, airflow and air velocity. The sensors may relay information to the computer system and control panel. The valves, fans and pumps may be automatically controlled by the results from the sensors. For example, if the concentration of fumigation gas in the flexible duct reaches a certain level, the valve will close and then the axial fan will turn off etc. Wireless devices may be used to communicate between the electronic devices in the gas extraction, dilution and dispersion system.

The power supply system may include a mains power source, a generator, a generator silencer and/or a battery. The generator may power devices including the dispersion fan, the axial fan, electronically actuated valves and/or other electronic devices in the gas extraction, dilution and dispersion system. A substantial portion of the gas received by the dispersion fan inlet comprises a chamber gas such that the ratio of chamber gas to fresh air may be between 1:5 and 1:20. Preferably the ratio can be between 1:7 and 1:15. Most preferably it is a ratio of about 1:14 to 1:15 parts of chamber gas to fresh air.

Another particular aspect of the invention provides:

The above mentioned gas exhaust and dispersion system for connection to a gas chamber temporarily sealed to the exterior environment and requiring chamber gas in the chamber to be extracted therefrom and diluted, including: an exhaust device including: an intake port adapted to be connected to the gas chamber through which chamber gas is extracted from the gas chamber; a relief port connected to the gas chamber, preferably on; the opposite side of the gas chamber to the intake port; a relief port valve to stop, slow or allow the flow of gas through the relief port; a flexible tube connected to the intake port; an axial fan to suck the chamber gas out of the chamber and blow the chamber gas out of the flexible tube; and a flexible tube valve to stop, slow or allow the flow of gas through the flexible tube; dispersion device including: a support structure; a dispersion fan mounted to the support structure; an exterior environment gas intake, which receives air from the environment surrounding the dispersion device; a flexible tube chamber gas intake, which receives air from the output of the flexible tube; and an inlet, which the exterior environment gas intake and flexible tube chamber gas intake lead into; and an outlet to the dispersion fan; wherein, the outlet of the dispersion fan is exposed to the exterior environment; wherein, the inlet to the dispersion fan sucks in gas from the exterior environment and the chamber gas comes out of the flexible tube and is added to the stream of gas from the exterior environment; wherein, the dispersion fan is positioned such that the output is facing vertically; and wherein, the dispersion fan is a high velocity fan, capable of displacing a substantial portion of the air received by the inlet.

Another particular aspect of the invention provides: A gas exhaust and dispersion system for extracting a chamber gas from a gas chamber temporarily sealed to the exterior environment, the system including: an exhaust device including: an intake port connected to the gas chamber through which chamber gas is extracted from the gas chamber; a relief port connected to the gas chamber, preferably on the opposite side of the gas chamber to the intake port; a relief port valve to stop, slow or allow the flow of gas through the relief port; a flexible tube connected to the intake port; and a flexible tube valve to stop, slow or allow the flow of gas through the flexible tube; a dispersion device including: a support structure; a dispersion fan mounted to the support structure; an exterior environment gas intake, which receives air from the environment surrounding the dispersion device; a flexible tube chamber gas intake, which receives air from the output of the flexible tube; and an inlet, which the exterior environment gas intake and flexible tube chamber gas intake lead into; an outlet to the dispersion fan; wherein, the outlet of the dispersion fan is exposed to the exterior environment; wherein the inlet of the dispersion fan sucks in gas from the exterior environment and the chamber gas is sucked out of the flexible tube and added to the stream of gas from the exterior environment through the venturi effect; wherein the dispersion fan is positioned such that the output is facing vertically; and wherein the dispersion fan is a high velocity fan, capable of displacing a substantial portion of the air received by the inlet of the dispersion fan at least 50m vertically in still and low humidity climatic conditions.

Another particular aspect of the invention provides: A gas exhaust or extraction, and dilution and dispersion system for extracting a chamber gas from a gas chamber temporarily sealed to the environment including: an extraction device including: an inlet port adapted to be connected to the gas chamber through which chamber gas is extracted from the gas chamber; and a relief port adapted to be connected to the gas chamber and spaced from the inlet port; a dispersion device including: a dispersion fan mounted on or to a support structure; an exterior inlet adapted to receive air from the environment surrounding the dispersion device; a flexible duct inlet adapted to receive air from the output of the flexible duct; and a dispersion fan inlet; and an outlet for the dispersion fan a control system adapted to control at least one component included in the gas extraction, dilution and dispersion system; and a power supply system adapted to power at least one component included in the gas extraction, dilution and dispersion system; wherein: the dispersion fan inlet is adapted to be in fluid communication with the exterior inlet and the flexible duct inlet, such that the exterior inlet and the flexible duct inlet lead into the dispersion fan inlet; the dispersion fan outlet is exposed to the exterior environment; the dispersion fan inlet is adapted to draw gas from the exterior environment and to draw the chamber gas from the flexible duct whereby to form a combined stream of gas from the exterior environment and chamber gas from the flexible duct; the dispersion fan is position able such that the dispersion fan outlet is adapted to deliver the combined stream of gas substantially upwardly; and the dispersion fan has a high velocity capacity, capable of displacing a substantial portion of the gas received by the dispersion fan inlet upwardly in a plume

Another particular aspect of the invention provides: A method of extracting a target fumigant gas from a gas chamber using the gas exhaust or extraction, and dilution and dispersion system described in one of the aforementioned statements of invention, including steps of: turning on a first turbomachine, such as an extraction fan in the form of an axial fan; turning on a second turbomachine in the form of a dispersion fan; leaving the extraction, dilution and dispersion system components in the current configuration for a predetermined length of time to reduce the target gas concentration in the gas chamber down to safe level based on a workplace exposure standard (WES) for the fumigant; turning off the first turbomachine; and turning off the second turbomachine. wherein, at least one of the above steps is controlled using the control system and power supply system.

In one particularly preferred example, the fumigant includes methyl bromide. In this example, the fumigant is diluted from a value of the order of 1,000 to 30,000ppm at the inlet to the first turbomachine (such as the extraction or axial fan) down to a level of about 5-50 ppm at the outlet to the second turbomachine (such as the dispersion fan), and most preferably between >0 ppm - 1 ppm through to about 5 ppm at the outlet, and after one hour of operation of the system, preferably down to below a threshold of 0.3ppm, and most preferably an undetectable level. The concentrations mentioned herein are specific to the target gas being Methyl Bromide, but a skilled person will appreciate that different target gases will involve different pre-operation levels and require different dilution targets for maintenance of safe levels of target gas in the immediate environment of the gas chamber and the system.

Advantageously, the system in its various forms used according to the various methods described herein lowers the concentration of fumigant in the gas chamber. In the case of the target gas being Methyl Bromide in the fumigation chamber, the system may disperse the Methyl Bromide into the atmosphere without exceeding the 1-hour Tolerable Exposure Limit (1 hour TEL) that equates to 0 - 0.3ppm of target gas in the surrounding atmosphere after one hour. Alternatively, one may make reference to the Workplace Exposure Limit (WES), which stipulates a level of 0 - 5ppm after 8 hours) in the surrounding atmosphere following ventilation of the gas chamber. Typically, the gas chamber for treating log rows is formed using a tarpaulin cast over a typical consignment of logs, or the gas chamber may comprise a ship hold to provide the sealable chamber.

In another aspect, the invention provides a method of extracting a target gas from a gas chamber, including steps of: forming a sealed gas chamber to define a space for fumigation of at least one item; connecting to the gas chamber a system, having a first component comprising a chamber gas exhaust or extraction apparatus and a second component having a dilution and dispersion apparatus, by an inlet providing an inlet to the system; providing a flexible duct between the first and second components; supplying a fumigant to the gas chamber and fumigating the item; turning on a first turbomachine of the first component to provide positive pressure to the duct; turning on a second turbomachine of the second component to dilute and disperse the chamber gas; and leaving the first and second turbomachines on for a period of time until the fumigant is diluted and dispersed. wherein, at least one of the above steps is controlled using the control system and power supply system.

In yet another aspect, the invention provides a method of extracting a target gas from a gas chamber, including steps of: providing a gas-removal system adapted to remove gas from a gas chamber filled with the gas; connecting the gas chamber to a dilution-dispersion-means to allow the gas in the gas chamber to be removed from the chamber to the dilution-dispersion-means by the removal system; diluting the gas by the dilution and dispersion means; and displacing a substantial portion of the gas as diluted gas into atmosphere outside the gas chamber in an upwardly directed plume in the atmosphere.

In another aspect, the invention may provide a method of extracting gas from a fumigation gas chamber using a gas exhaust and dispersion system including the following steps: turning on a generator to supply electrical power to a first turbomachine and to a variable speed drive. turning on a second turbomachine having a substantially higher volumetric capacity than the first turbomachine, its operation governed by the variable speed drive, whereby the variable speed drive sets a rotational speed of the second turbomachine; turning on the first turbomachine to create a positive pressure in a flexible duct interposed between an inlet of the system and an inlet to the second turbomachine, drawing gas out of the chamber result in a negative pressure (compared to atmospheric pressure) in the gas chamber 62; diluting the chamber gas and blowing it upwardly in a plume whereby to disperse the diluted gas into the atmosphere.

In another aspect, the invention provides a method of extracting gas from a fumigation gas chamber in the form of a ship hold using a system comprising an exhaust or extraction component, and dilution and dispersion component, including the following steps: using a first manway communicating the ship hold to the deck as an inlet to the system and using a second access to the ship hold as a relief port; positioning the dilution and dispersion component near the inlet; connecting a first turbomachine to a bulk head of the inlet; and providing a flexible duct between the first turbomachine and the inlet, the flexible duct also functioning as a flexible duct valve by being collapsible and adapted to folds under its own weight to adequately seal the gas inside the gas chamber and prevent it from diffusing out of the gas chamber. One end of the flexible duct 56 is connected to the axial fan 54 and the other end is connected to the flexible duct inlet 22.

The system may include valves to regulate flow in the system, including reducing the incidence of backflow. The valves may be found in the relief port and the inlet port. The valves may be actuated electronically. Preferably, the valves are actuated manually. The electronic actuation through the control system and power supply system may include control signals sent from an electronic user interface. The control signals may be sent to the actuating valve device using wired or wireless connections. The electronic user interface may include buttons, a touch screen panel and/or remote communication through wireless devices such as a user’s mobile phone. The power supply system may be controlled by the control system. The power supply system may power the actuation of the valves, the axial fan, the dispersion fan and the control system. Preferably, the power supply system controls the axial fan and the dispersion fan.

Another particular aspect of the invention provides: A gas extraction or exhaust, and disposal or dispersion system for removing a chamber gas from a gas chamber temporarily sealed from the exterior environment, the system including: an extraction device including: an inlet port adapted to be connected to the gas chamber through which chamber gas is extracted from the gas chamber; a relief port adapted to be connected to the gas chamber and spaced from the inlet port; a relief port valve to stop, slow or allow the flow of gas through the relief port; a flexible duct adapted to be connected to the inlet port; an axial fan installed near the inlet port end of the flexible duct and adapted to create a positive pressure in the flexible duct; and a flexible duct valve installed at any point along the flexible duct and adapted to stop, slow or allow gas to flow through the flexible duct; a dispersion device including: a dispersion fan mounted on a support structure; an exterior inlet adapted to receive air from the environment surrounding the dispersion device; a flexible duct inlet adapted to receive air from the output of the flexible duct; a dispersion fan inlet, which receives air from the exterior inlet; a dispersion fan outlet; a control system adapted to control at least one device in the gas exhaust and dispersion system; a power supply system adapted to power at least one component included in the gas exhaust and dispersion system; a dilution zone, in which gas from the dispersion fan outlet and flexible duct inlet is combined and mixed; a dilution zone housing; wherein, the dispersion fan draws, drives and/or pushes the gas in the dilution zone substantially upwardly out of the dilution zone at a velocity of at least 15 m/s.

The relief port valve may be an attachment to the relief port. Preferably, the relief port valve is included in the relief port. The flexible duct valve or inlet portal valve may be included in the inlet port. The inlet port valve may be attached to the inlet port or included in the flexible duct. The flexible duct valve may be attached to the end of the flexible duct, connecting the flexible duct to the flexible duct inlet. Preferably, the inlet port includes an arch shaped exterior surface whereby to house the inlet portal valve.

The axial fan is preferably in the form of a turbomachine. The axial fan may also be referred to as a first turbomachine. The first turbomachine may have a lower volumetric flow rate capacity than the dispersion fan. The first turbomachine may have a similar volumetric flow rate capacity compared to the dispersion device, which may be referred to as a second turbomachine. Preferably, the first turbomachine has a lower volumetric flow rate capacity than the second turbomachine. However, at the inlet to the first turbomachine, preferably the first turbomachine is adapted to generate a higher pressure at the first inlet than the second turbomachine generates at the inlet zone to the second turbomachine.

The first and second turbomachines, the axial or extraction fan, and the dispersion fan, may each comprise a compressor, other types of air pumps, a positive displacement pump or other turbomachinery which may be used to increase pressure in a constricted or contained space, such as the gas chamber, the inlet port or flexible duct. Preferably, the dispersion fan has at least twice the volumetric flow rate of the extraction or axial fan. Most preferably, the dispersion fan has at least 10 times the volumetric flow rate capacity of the axial fan. For example, preferably the dispersion fan achieves a flow rate of between 100,000 and 300,000m3/h.

The dilution zone housing may form a circumferential structure around or surrounding at least one portion of the dilution zone. Preferably, the dilution zone housing substantially encloses the dilution zone.

The dilution zone housing may include a cylinder. The cylinder may include a taper in the longitudinal direction. The taper may follow a straight line or a curved line. A portion or all of the cylinder may include a venturi, or a narrowing of the cylinder’s internal diameter. The venturi portion of the dilution zone housing may include a first set of dilution zone pipes or tubes leading into the cylinder just downstream of the contraction in the cylinder. The first set of dilution zone pipes or tubes may lead into at least one nozzle attached to the cylinder, such that gas flowing through the first set of dilution zone tubes or pipes is pumped out of the nozzles into the dilution zone at high velocities, for example greater than 15 m/s. The air out of the nozzles or first set of dilution zone pipes or tubes may propel the gas inside the dilution zone at high velocity (at least 15 m/s) out of the dilution zone.

The propulsion of gas out of the dilution zone from the nozzles or tubes may cause a venturi in the dilution zone. The compressor may pump air at high pressure out of nozzles in a location just upstream of the narrow neck or waste of the cylinder in the dilution zone housing. The venturi in the dilution zone may create a negative pressure in regions upstream of the nozzles. A second set of dilution zone pipes or tubes may lead into these negative pressure regions and gas may be sucked out of these tubes or nozzles. The flexible duct outlet may lead into the first set of dilution zone pipes or tubes and the dispersion fan inlet may lead into the second set of dilution zone pipes or tubes. The dispersion fan inlet may lead into the first set of dilution zone pipes or tubes and the flexible duct inlet may lead into the second set of dilution zone pipes or tubes.

The dilution zone housing may form an eductor. For example, the dilution zone housing may include a cylinder or tube with inlet pipes on the sides.

Preferably, the velocity of the gas exiting the dilution zone is between 15 m/s and 35 m/s. Most preferably, the velocity of the gas is between 27m/s and 30 m/s.

The dispersion fan outlet may include at least one nozzle or tube leading into the dilution zone. The compressor or pump may pump air into the lowest portion of the dilution zone housing forming a stream of air in the dilution zone and chamber gas may be blown into this stream through ports in the side of the dilution zone housing. Therefore, the dispersion fan or second turbomachine and dilution zone housing may include an eductor, adapted to draw a second fluid into a passage carrying a first moving fluid.

The dispersion fan may be in the form of a turbomachine and the dispersion fan may be described as a second turbomachine. The dispersion fan may be an air moving device, such as a propeller or a high powered fan. The dispersion fan may include guide vanes or fan louvres to direct the flow of gas into, out of and/or around the dispersion fan. The dispersion fan may include a diffuser, for example to diffuse or disperse the gas from the flexible duct inlet into the dilution zone. The dispersion fan may be situated inside the dilution zone. The dispersion fan may be situated outside the dilution zone housing, for example with a pipe leading from the dispersion fan to the outlet of the dispersion fan on the dilution zone housing or inside the dilution zone. The dispersion fan may be situated above the dilution zone. The dispersion fan may be situated below the dilution zone. Preferably, the dispersion fan includes a impellor and an electric motor and is situated above the dilution zone, wherein, gas in the dilution zone is drawn into the dispersion fan and blown upwardly out of the dispersion fan outlet. In another aspect, the dispersion fan may be adapted to pump the ex-fumigation gas received from the flexible duct into a trap or sink for storage.

The dilution zone housing may include support beams or other components necessary to hold, control and power the dispersion fan. The dilution zone housing may be generally cylindrically shaped to provide a cylinder. The cylinder may include a tapered portion surrounding the outlet of the dilution zone housing such that the cylinder tapers down to a minimum circumference at the outlet end.

The support structure may support the dispersion fan. The support structure may further support the control system and the power supply system. The support structure may include slots, rings or holes which may provide channels to receive forks of a lifting device such as a fork lift.

The dispersion fan inlet for the second turbomachine inlet may include the portion of the dilution zone housing below the second turbomachine. The second turbomachine inlet may include the region or area of gas below the second turbomachine which significantly contains the stream of gas drawn in by the second turbomachine. The second turbomachine inlet may include a cylinder or enclosed duct directly below the second turbomachine. The second turbomachine may provide or constitute the exterior inlet. The second turbomachine inlet may include the junction tube/pipe/duct where the exterior inlet and the flexible duct inlet meet. Preferably, the second turbomachine inlet includes the cylinder or enclosed duct directly below the second turbomachine.

The outlet of the second turbomachine may include the portion of the dilution zone housing above the second turbomachine. The outlet of the second turbomachine may include the region of gas above the second turbomachine which significantly contains the stream of gas exiting the second turbomachine. The outlet of the second turbomachine may include other ducts or pipes attached to the dilution zone housing above the second turbomachine. The outlet of the second turbomachine may include a mesh screen. The outlet of the second turbomachine may include channels, fins or guide vanes which direct and maintain the stream of gas coming out of the second turbomachine. Preferably, the outlet of the second turbomachine includes the portion of the dilution zone housing above the second turbomachine and a mesh screen.

Another particular aspect of the invention provides: A gas extraction or exhaust, and dispersion system including: a gas chamber, sealed to the exterior environment; an extraction device including: an inlet port adapted to be connected to the gas chamber through which chamber gas is extracted from the gas chamber; a relief port adapted to be connected to the gas chamber and spaced from the inlet port; a relief port valve to stop, slow or allow the flow of gas through the relief port; a flexible duct adapted to be connected to the inlet port; a flexible duct valve adapted to stop, slow or allow gas to flow through the flexible duct; a dispersion device including: a support structure; an exterior inlet adapted to receive air from the environment surrounding the dispersion device; a flexible duct inlet adapted to receive gas from the output of the flexible duct; a second turbomachine upstream of the exterior inlet; a dilution zone, in which gas from the exterior inlet and flexible duct inlet is combined and mixed; a dilution zone inlet, which receives gas from the exterior inlet and flexible duct inlet; a dilution zone outlet, through which combined gas exits at high velocity; a control system adapted to control at least one device in the gas exhaust and dispersion system; and a power supply system adapted to power at least one component in the gas exhaust and dispersion system; wherein, an outlet of the second turbomachine is adapted to be in fluid communication with the dilution zone, such that the second turbomachine draws, drives or pushes the gas in the dilution zone substantially upwardly out of the dilution zone outlet at a velocity of at least 15 m/s.

The power supply system may power the actuation of the valves, the axial fan, the second turbomachine and the control system. Preferably, the power supply system supplies power to the axial fan and the second turbomachine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood from the following non-limiting description of preferred embodiments, in which:

Figure 1 is an isometric front view of a dispersion device;

Figure 2 is a rear cross sectional view of the dispersion device;

Figure 3 is a top isometric view of an inlet port; and

Figure 4 is an isometric view of a gas exhaust or extraction, and dispersion system showing components which extract gas from a chamber connected to a first position on a tarpaulin (on the right side) and a relief valve to allow ingress of air that is connected to a second position on a tarpaulin (on the left side); and

Figure 5 is a schematic side view of a gas exhaust or extraction, and dispersion system for a ship hold application.

DETAILED DESCRIPTION OF THE DRAWINGS

Preferred features of embodiments of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention, except as may be recited in the claims accompanying this specification.

Referring to the accompanying drawings, a gas extraction or exhaust, and dilution and dispersion system including a gas chamber 62 sealed to the exterior environment 66, and removal-means which includes a first propulsion means which may act as an extraction device. The extraction device includes an inlet port 40a adapted to be connected to the gas chamber 62 through which chamber gas is extracted from the gas chamber 62, a relief port 40b adapted to be connected to the gas chamber 62 and spaced from the inlet port 40a, a relief port valve 52b to stop, slow or allow the flow of gas through the relief port 40b, a flexible duct 56 adapted to be connected to the inlet port 40a, a first turbomachine (such as an axial fan) 54 between the inlet port 40a and the flexible duct 56 and adapted to create a positive pressure in the flexible duct 56, and a flexible duct valve 52a adapted to stop, slow or allow the flow of gas through the flexible duct 56. The system further includes a second propulsion means or turbomachine acting as a dilution-dispersion-means that includes a dispersion device 20. The dispersion device 20 includes a support structure 21, an exterior inlet 24 adapted to receive gas from the environment 66 surrounding the dispersion device 20, a flexible duct inlet 22 adapted to receive air from the output of the flexible duct 56, a second turbomachine (dispersion fan), 25,26 upstream of the exterior inlet 24, a dilution zone 70, in which gas from the exterior inlet 24 and flexible duct inlet 22 is combined and mixed, a dilution zone inlet 29, which receives gas from the exterior inlet 24 and flexible duct inlet 22, a dilution zone outlet 28, through which combined gas exits at a high velocity of at least about 15 m/s, a control system 34 adapted to control at least one device in the extraction system; and a power supply system 30 adapted to power at least one component in the gas exhaust and dispersion system. A second turbomachine outlet is adapted to be in fluid communication with the dilution zone 70, such that the second turbomachine draws, drives or pushes the gas in the dilution zone 70 substantially upwardly out of the dilution zone outlet 28 at a velocity of at least 15 m/s, and ideally between about 26 to about 30 m/s.

In one form of the invention shown in Figures 1 to 4, the gas chamber is a tarpaulin 62. The tarpaulin 62 is sealed using a water filled tube 64 forming a bead that is laid over the tarpaulin 62 around the circumference, periphery or edge of the tarpaulin 62. The tarpaulin 62, sealed at its sealed edges where that portion of the tarpaulin 62 meets a substrate, such as the ground, or a deck or tarmac 61, forms a gas chamber which may receive a fumigation gas, such as Methyl Bromide.

The inlet port 40a and the relief port 40b are placed underneath the tarpaulin 62 and the water filled tube 64 spaced apart from each other. Preferably, the inlet port 40a and the relief port 40b are located on opposing sides of the tarpaulin such that they are at a maximum distance away from each other. The portion of the water filled tube 64 over each of the ports is malleable or mouldable to the contours of the ports and holds a significant weight. The bead 64 therefore presses down on the tarpaulin 62, creating a seal between the tarpaulin and the ports, the ports and the substrate 61 and the tarpaulin 62 and the substrate 61. The seal achieves minimal or insignificant leakage of fumigation gas and therefore is substantially sealed.

The inlet port 40a and relief port 40b are the identically designed and shaped. Port 40 is shown in FIG. 3. The port 40 that is adapted to be used in the gas exhaust and dispersion system includes a channel 47, a channel inlet 44 and a channel outlet 42. A compression device 64 is placed over a portion of flexible wall 62 on the top face of the inlet port 40 and baffles 45 are inserted into the channel 47 to support the outer shell. The baffles 45 may also facilitate the flow through the channel 47. Handles or lugs 48a and 48b are provided on the sides of the port 40 to assist in its manual handling or mechanical lifting. The channel inlet 44 has a rectangular cross section and the channel outlet 42 has a cylindrical cross section.

The flexible duct valve 52a is attached to the inlet port 40a and the relief port valve 52b is attached to the relief port 40b. The flexible duct valve 52a and the relief port valve 52b are manually operated butterfly valves.

The first turbomachine or axial fan 54 is attached to the flexible duct valve 52a. The axial fan 54 is used to create a positive pressure in the flexible duct 56. The low pressure at the dispersion fan or second turbomachine inlet 29 reduces the pressure in the flexible duct 56, therefore sucking in gas from the gas chamber 62. The low pressure in the flexible duct 56 would apply a crushing force to the flexible duct 56. Flexible tubing is generally not designed for handling very low pressures but it is required or at least very advantageous to use flexible tubing given the portable nature of the system. Therefore, the axial fan 54 reduces the crushing pressure on the flexible duct 56.

The flexible duct 56 attaches to the flexible duct inlet 22 on the dispersion device 20. The dispersion device 20 may be lifted into the required position using a forklift with the forks inserted through slots 21a in the support structure 21. The support structure 21 supports every component of the dispersion device 20 either directly or indirectly. A power cable 55 coming from the diesel generator 32 powers the axial fan. The power supply system 30 includes the diesel generator 32 and a generator silencer 36. The control system 34 includes a variable speed drive to control the speed of the dispersion fan. The dispersion fan includes a propeller 25 and an electric motor 26. The dispersion fan is enclosed by a dispersion fan housing 27 which includes a cylindrical shell with a tapered outer circumferential face, the taper leading to a minimum outer diameter at the dispersion fan outlet 28.

The propeller 25 and electric motor may be accessed through an access port 23.

The method of extracting gas from a fumigation gas chamber 62 using the gas exhaust and dispersion system includes the following steps:

Turn on the diesel generator 32. This supplies electrical power to the axial fan 54 and the variable speed drive.

Turn on the dispersion fan through adjusting controls on the variable speed drive 34. This step involves setting the rotational speed of the dispersion fan. At this stage the dispersion fan is sucking in gas from the exterior environment 66 through the exterior inlet 24 into the dispersion fan inlet 29 and out of the dispersion fan outlet 28 at a high velocity of about 27 - 30m/s. The exterior inlet 24 and dispersion fan outlet 28 includes a mesh screen to protect equipment and personnel operating the system. The gas is blown upwardly in a plume at least 50m.

Turn on the axial fan 54 through a switch on the axial fan 54 creating a positive pressure in the flexible duct 56.

Actuate the flexible duct valve 52a manually so that chamber gas may pass through the flexible duct 56. Chamber gas then enters the dispersion fan inlet 29 and combines with the gas from the exterior environment with a dilution of approximately 1 part chamber gas to 14 parts exterior environment gas in the gas out of the dispersion fan outlet 28. The diluted chamber gas is blown upwardly in the plume and dispersed into the atmosphere. The axial fan and the dispersion fan sucking gas out of the chamber result in a negative pressure (compared to atmospheric pressure) in the gas chamber 62.

It is now safe to actuate the relief port valve 52b manually so that gas may pass through the relief port 40b, so that no chamber gas will exit through the relief port 40b.

Leave components in the current configuration for a predetermined length of time, which will be determined based on the volume and dimensions of the gas chamber 62 and the rate at which the gas is extracted from the gas chamber. The concentration of chamber gas in the gas chamber will now be insignificant. Actuate the relief port valve 52b manually so that gas cannot pass through the relief port 40b.

Actuate the flexible duct valve 52a manually so that chamber gas may pass through the flexible duct 56.

Turn off the axial fan 54 via the switch on the axial fan 54. Turn off the dispersion fan via the variable speed drive.

Turn off the generator.

In a second form of the invention the gas chamber is a ship hold. The ship hold is substantially sealed to the exterior environment and filled with a fumigation gas, again

Methyl Bromide is often used.

The inlet port and the relief ports are manholes, preferably located on opposite ends of the ship hold. A bulkhead is placed over or inside the manhole which forms an attachment directly to the flexible duct or preferably, to the axial fan. The dispersion device 20 is the same as the first form of the invention. The dispersion device 20 may be placed on the ship or off the ship, for example on a wharf. A method of extracting gas from a fumigation gas chamber 62, wherein the fumigation gas chamber 62 is a tarpaulin 62 over a log row, using the gas exhaust and dispersion system includes the following steps:

The dispersion device 20 is positioned near the inlet port 40a.

The flexible duct valve 52a and the relief port valve 52b are configured to stop the flow of gas through the valves.

The flexible duct valve 52a and the relief port valve 52b are attached to the inlet port 40a and relief port 40b respectively.

The inlet port 40a and the relief port 40b are positioned between the tarpaulin 62 and the substrate 61 at locations on opposite sides of the tarpaulin and operators ensure the water filled duct 64 is directly over both of the valves.

The axial fan 54 is connected to the flexible duct valve 52a.

One end of the flexible duct 56 is connected to the axial fan 54 and the other end to the flexible duct inlet 22.

The power cable 55 coming from the diesel generator 32, via the control system 34 is connected to the axial fan 54. Wherein, the control system 34 includes another variable speed drive for the axial fan 54 and other controls to control the operation of the axial fan 54.

The diesel generator 32 is turned on and the operator waits for the generator 32 to complete a self-check and for the variable speed drives on the control system 34 to initiate.

The operator initiates the start-up program in the control system 34 for the dispersion fan, which turns on the dispersion fan, 25 and 26, and takes flow sensor readings, taken from within the dilution zone 70 and observed from the control system, to ensure the readings are within a permissible zone.

The flexible duct valve 52a is manually configured to allow flow of gas through the valve 52a.

The operator initiates the start-up program in the control system 34 for the axial fan 54.

The operator waits for negative pressure to reach a certain level within the gas chamber 62.

The relief port valve 52b is manually configured to allow flow of gas through the valve 52b.

The operator observes the control system 34 to ensure flow readings from the axial fan 54 and the dispersion fan, 25 and 26, are within permissible zones and makes any adjustments to the variable speed drives necessary.

After the predetermined length of time the relief port valve 52b is manually configured to stop the flow of gas through the valve.

The flexible duct valve 52a is manually configured to stop the flow of gas through the valve.

The axial fan 54 is turned off at the control system 34.

The dispersion fan, 25 and 26, is turned off at the control system 34.

The diesel generator 32 is turned off.

With reference to Fig. 5, there is shown a system for extracting gas from a fumigation gas chamber that is specific to a ship hold fumigation gas chamber 62. Use of the system involves a method including the following steps:

The inlet port 40a and relief port 40b include manways into the ship hold. The relief port 40b includes the man way which contains the Australian ladder and a duct which is connected to the man way and run down into the ship hold behind the Australian ladder. The inlet port 40a includes the man way which contains the straight ladder.

The relief port valve 52b is the lid on the manway containing the Australian ladder and is closed to stop the flow of gas through the valve.

The inlet port 40a also includes an inlet bulkhead which is installed on the manway which contains the straight ladder.

The dispersion device 20 is positioned near the inlet port 40a.

The axial fan 54 is connected to the inlet bulk head.

The flexible duct 56 also functions as the flexible duct valve 52a because the flexible duct 56 is a collapsible piece of material which folds under its own weight capable of adequately sealing the gas inside the ship hold from diffusing out of the ship hold. One end of the flexible duct 56 is connected to the axial fan 54 and the other end is connected to the flexible duct inlet 22.

The power cable 55 coming from the diesel generator 32, via the control system 34 is connected to the axial fan 54. Wherein, the control system 34 includes a variable speed drive for the axial fan 54 and other controls to control the operation of the axial fan 54.

The diesel generator 32 is turned on and the operator waits for the generator 32 to complete a self-check and for the variable speed drives on the control system 34 to initiate.

The operator initiates the start-up program in the control system 34 for the dispersion fan, which turns on the dispersion fan, 25 and 26. The control system 34 takes flow sensor readings, taken from within the dilution zone 70 and observed from the control system, to ensure the readings are within a permissible zone.

The operator initiates the start-up program in the control system 34 for the axial fan 54.

The operator waits for negative pressure to reach a certain level within the gas chamber 62.

The relief port valve 52b is configured manually to allow flow of gas through the valve 52b or more specifically, the man way containing the Australian ladder is opened.

The operator observes the control system 34 to ensure flow readings from the axial fan 54 and the dispersion fan, 25 and 26, are within permissible zones and makes any adjustments necessary.

After the predetermined length of time the man way containing the Australian ladder is closed.

The axial fan 54 is turned off through the control system 34.

The dispersion fan, 25 and 26, is turned off through the control system 34.

The diesel generator 32 is turned off.

Throughout the specification and claims the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word “comprise” and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

In the present specification, terms such as “apparatus”, “means”, “device” and “member” may refer to singular or plural items and are terms intended to refer to a set of properties, functions or characteristics performed by one or more items or components having one or more parts. It is envisaged that where an “apparatus”, “means”, “device” or “member” or similar term is described as being a unitary object, then a functionally equivalent object having multiple components is considered to fall within the scope of the term, and similarly, where an “apparatus”, “assembly”, “means”, “device” or “member” is described as having multiple components, a functionally equivalent but unitary object is also considered to fall within the scope of the term, unless the contrary is expressly stated or the context requires otherwise.

Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the dispersion device 20 uppermost.

In construing the term “extraction” device, including apparatus, system and means, it will be understood that the extraction device is operable to urge chamber gas to be removed from the gas chamber.

The term “fumigation” is understood in the context of this specification, to mean the removal of the chamber gas, including the target gas, from the gas chamber.

It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention.

Claims (20)

1. The Claims defining the invention are as follows:

   1. A gas-removal system adapted to remove gas in the form of chamber gas from a gas chamber filled with the chamber gas, including: dilution-dispersion-means adapted to displace the gas into atmosphere outside the gas chamber; removal-means adapted to connect the gas chamber to the dilution-dispersion-means to allow the gas in the gas chamber to be removed from the gas chamber via the removal-means to the dilution-dispersion-means, and displaced by the dilution-dispersion-means into the atmosphere; wherein the dilution-dispersion-means includes propulsion-means capable of displacing a substantial portion of the ex-chamber gas in an upwardly directed plume so that the gas is at least capable to being diluted high in the atmosphere; and the removal means is in the form of an extraction device which includes: an inlet port adapted to be connected to the gas chamber containing gas in the form of chamber gas to be extracted and to receive ex-chamber gas from the gas chamber; a flexible duct adapted to be connected to the inlet port; an extraction fan installed near or in the inlet port and adapted to create a positive pressure in the flexible duct.
2. 2. The system of claim 1, wherein: the dilution-dispersion-means includes a dilution and dispersion device; and the propulsion-means comprises a dispersion fan.
3. 3. The system of claim 2, wherein the dilution and dispersion device includes: a dispersion fan mounted on a support structure; an air inlet adapted to receive air from the environment surrounding the dilution and dispersion device whereby to dilute a stream of the exchamber gas exiting the extraction device; a dilution and dispersion device inlet adapted to receive air from the output of the flexible duct; a dispersion fan inlet zone; a dispersion fan outlet; a control system adapted to control at least one device in the extraction, and dilution and dispersion devices; and a power supply system adapted to power at least one component included in the extraction, and dilution and dispersion devices; wherein: the dispersion fan inlet zone is adapted to be in fluid communication with the air inlet and the flexible duct outlet, such that the air inlet and the flexible duct outlet lead into the dispersion fan inlet zone; the dispersion fan is adapted to draw gas from the exterior environment and the exchamber gas from the flexible duct outlet whereby to form at the dispersion fan inlet zone a combined stream of diluted gas comprising atmospheric air from the exterior environment and ex-chamber gas from the flexible duct; the dispersion fan outlet is exposed to the exterior environment; the dispersion fan outlet is adapted to deliver the combined stream of diluted gas substantially upwardly; and the dispersion fan has a high velocity capacity, capable of displacing a substantial portion of the ex-chamber gas received by the dispersion fan inlet zone in an upwardly directed plume.
4. 4. The system according to Claim 3, wherein the chamber gas includes methyl bromide.
5. 5. The system according to Claim 3 or 4, wherein the flexible duct is collapsible and/or foldable for easy transport and storage.
6. 6. The system according to any one of claims 3-5, wherein the dispersion fan has at least 10 times the volumetric flow rate capacity of the extraction fan.
7. 7. The system according to any one of claims 3-6, wherein the gas removal system is portable.
8. 8. The system according to any one of claims 3-7, wherein the flexible duct outlet is positioned under the dispersion fan inlet zone, whereby the dispersion fan inlet zone is adapted to receive the combined stream of diluted gas being drawn into the dispersion fan inlet zone.
9. 9. The system according to any one of claims 3-8, wherein the dispersion fan inlet zone includes a Y-junction duct where an atmospheric air inlet and the flexible duct outlet meet.
10. 10. The system according to any one of claims 3-9, wherein the dispersion fan comprises a dispersion fan housing and the dispersion fan inlet zone includes a mesh screen to prevent objects entering the dispersion fan housing.
11. 11. The system according to any one of claims 3-10, wherein the control system includes a variable speed drive to control a motor powering the dispersion fan, a control panel to provide a user interface to operate all the electronics in the extraction, and dilution and dispersion devices, and a computer system.
12. 12. The system according to Claim 11, wherein the control system also includes sensors including for temperature, chemical composition, pressure and/or air velocity.
13. 13. The system according to any one of claims 3-12, wherein the power supply system includes a generator and a generator silencer for powering the dispersion fan, the extraction fan, and at least one electronically actuated valve.
14. 14. The system according to any one of claims 3-13, wherein the dispersion fan includes a dilution zone and draws, drives and/or pushes the combined stream of diluted gas in the dilution zone substantially upwardly out of the dilution zone at a velocity of at least 15 m/s.
15. 15. The system according to any one of claims 3-13, wherein the extraction and the dispersion fans are axial fans for direct displacement of gas inline, the velocity of the combined stream of diluted gas exiting the dispersion fan outlet is of the order of about 25 to about 30 m/s and the flexible duct outlet leads directly into the dispersion fan inlet zone.
16. 16. The system according to claim 14 or 15, wherein the dispersion fan housing includes the dilution zone and the dispersion fan housing forms a circumferential structure substantially enclosing the dilution zone.
17. 17. The system according to Claim 16, wherein the dilution fan housing includes a cylinder having an internal diameter such that there is a taper in the longitudinal direction, the dispersion fan housing including a venturi or a narrowing of the cylinder’s internal diameter.
18. 18. The system according to Claim 16 or 17, wherein the dilution fan housing forms an eductor.
19. 19. The system according to any one of Claims 16 to 18, wherein the dispersion fan inlet zone includes an enclosed duct directly below the dispersion fan.
20. 20. The system according to any one of claims 3-19, wherein the dispersion fan is a high velocity fan capable of displacing a substantial portion of the combined stream of diluted gas received by the inlet of the dispersion fan at least 50m vertically.