WO2016197202A1

WO2016197202A1 - Fumigant formulation and vaporising apparatus

Info

Publication number: WO2016197202A1
Application number: PCT/AU2016/050474
Authority: WO
Inventors: Simon MCKIRDY; Simon O'connor; James Patrick NEWMAN; Yonglin Ren
Original assignee: Innovative Biosecurity Pty Ltd
Priority date: 2015-06-12
Filing date: 2016-06-10
Publication date: 2016-12-15
Also published as: AU2016275572B2; AU2016275572A1

Abstract

A fumigant formulation and apparatus and method for application of the fumigant formulation. A diluent is heated to a temperature above boiling point of a liquid fumigant. Hot diluent is contacted with the liquid fumigant to increase temperature of the liquid fumigant sufficiently to form a vapour of liquid fumigant and diluent. The fumigant/diluent mixture is suitable for application to an area or volume requiring treatment and has particular use in treatment to control invertebrates.

Description

FUMIGANT FORMULATION AND VAPORISING APPARATUS

FIELD OF THE INVENTION

[0001 ] The present invention relates to a fumigant formulation and to an apparatus for vaporising a liquid fumigant and delivering insecticides, bactericides, fungicides and herbicides as a fumigant.

BACKGROUND TO THE INVENTION

[0002] Fumigants are volatile agents used to kill and control pests and pathogens. The term 'fumigant' generally refers to chemicals used for fumigation purposes. Fumigants are commonly used in agricultural/horticultural and biosecurity/quarantine applications. As an example, perishable commodities, in particular foodstuffs, can be at risk from infestation by invertebrates, typically insects, particularly when the commodity is stored in bulk quantities. Infestation frequently leads to economic losses as infested commodities may need to be discarded or sold for a less than premium price. Foodstuffs such as fruit and grains are particularly susceptible to infestation by invertebrates, though equipment and facilities can also experience infestation and are often treated by fumigation to control these pests. Similarly, warehouses, houses, ships, containers, silos, fruit trees, timber and soil may require treatment through fumigation to control various pathogens and pests.

[0003] There are a series of chemicals which are used for fumigation purposes. Insecticidal chemicals are typically used for control of invertebrate pests in agriculture/horticulture. Certain natural oil and plant extracts are employed as fumigants for use as herbicides. For control of insects in agriculture/horticulture, universally insecticidal fumigants are used. There are presently a somewhat limited number of fumigants widely available for use in agricultural/horticultural applications, particularly on consumable commodities such as foodstuffs. [0004] Use of fumigation technology is common and there are a number of available liquid fumigants available, including ethyl formate, hydrogen cyanide, calcium cyanide, carbon dioxide, sulphur dioxide, carbon tetrachloride, ethylene dichloride, ethylene bromide, p-dichlorobenzene and γ-BHC. Each of these liquid fumigants has certain advantages and disadvantages.

[0005] In control or prevention of invertebrate infestations, commonly used fumigants are methyl bromide and phosphine. Methyl bromide is a broad spectrum pesticide having non-specific toxicity to a wide range of invertebrates. Methyl bromide can have deleterious effects on humans and other animals if they are exposed to high concentrations. Methyl bromide dissipates rapidly into the atmosphere following application and is therefore most dangerous at the site of fumigation. Methyl bromide is also widely considered to be a known and significant ozone depleting substance. Whilst there are natural sources of methyl bromide, addition of it to the atmosphere via fumigation contributes to thinning of the ozone layer. The detrimental effects of ozone thinning are well known and documented.

[0006] Phosphine is often relied on for fumigation of grain and other similar commodities. Whilst effective if used properly, due to excessive reliance and improper application, there are increasing reports of resistance to phosphine. If resistance continues to increase, phosphine may eventually fail to provide a reliable fumigant in control of invertebrates.

[0007] Ethyl formate is a fumigant having properties that indicate usefulness as a fumigant, particularly in controlling invertebrates. Ethyl formate vapour has previously been shown to be toxic to insects common to infestation of stored commodities. Further, ethyl formate is a naturally occurring compound, which rapidly breaks down into harmless and naturally occurring products and has low human toxicity. These are features which indicate suitability particularly for treatment of food commodities. It is a liquid at normal ambient temperatures and has a boiling point of 54°C. However, ethyl formate is highly flammable, with 2.8% (v/v) or 92 g/m-³ of lower explosive limit (LEL). This poses a significant problem in practical use of ethyl formate as a fumigant as it is necessary to avoid conditions that can ignite a flame. Other fumigants useful in control of invertebrates, such as ethylene dichloride, also have similar flammability concerns with their use.

[0008] Due to flammability, application of ethyl formate and other flammable compositions as a fumigant requires careful operation to mitigate risk of ignition. Current practices try to avoid risk of ignition by, for example, mixing liquid ethyl formate and non-flammable gas in cylinders to form a non-flammable ethyl formate fumigant at high pressure. However, the practice of using gas in cylinders has the disadvantage of potential carburettor icing phenomenon, especially in warm or humid environments, which can increase application time significantly as the gas regulator becomes frozen. In addition, if cylinderised fumigants are used, well trained fumigant operators, appropriately trained in handling of high pressure cylinders, are required to apply the fumigant.

[0009] It is known that it is possible to create a substantially non-flammable fumigant at high pressure by combining liquid fumigant with carbon dioxide. The premise behind such a mixture is that carbon dioxide is provided in sufficient quantity to render the flammable liquid as non-flammable. However, fumigation systems based on fumigant mixed with carbon dioxide have all the limitations associated with using pressurised canisters. Further, use of carbon dioxide may cause undesirable degradation or corrosion of some materials, limiting the scope of use of such mixtures.

[0010] In order to apply liquid fumigants, a vaporiser is required to convert liquid to gas before the fumigant is introduced into a fumigation chamber, such as a standard shipping container. It is not desirable to apply liquid fumigant without vaporisation since levels of residual non-vaporised liquid fumigant can pose occupational health and safety hazards or cause damage to goods receiving treatment with the fumigant. Similarly, if vaporisation is incomplete or vaporised fumigant is applied to a treatment area or container substantially less than homogenously, goods can also become damaged due to settling of unvaporised liquid fumigant. Incomplete vaporisation or substantially less than homogenous application also leads to ineffectiveness of the fumigation process.

[0011 ] Design of vaporisers may vary, but generally consist of a water bath in which a length of tubing is immersed. The water is heated by a gas burner or electric element. Liquid fumigant is passed through the tubing, whereby heat in the water is transferred to the liquid fumigant through the walls of the tubing, causing the liquid fumigant to vaporise before it passes out of the vaporiser and into the area requiring fumigation.

[0012] Existing vaporiser designs generally require that the liquid fumigant be provided in a pressurised cylinder, which of itself introduces operational considerations already noted above and may limit the areas in which the fumigant can be applied. Further, existing vaporiser designs can demonstrate variability in ability to sufficiently heat the liquid fumigant, resulting in incomplete or partial vaporising of the liquid fumigant. This can result in inefficient and ineffective application of the fumigant, including non-homogenous distribution of fumigant throughout a treatment area. It can also pose a safety hazard, particularly if the liquid fumigant is toxic or hazardous to humans. There is therefore much need for improvement in fumigation technology, to expand the range of fumigants that can be safely and effectively used and to mitigate various operational inefficiencies and safety hazards.

[0013] The present invention seeks to provide a fumigant formulation having insecticidal, bactericidal and/or herbicidal fumigation capacity and to facilitate its application in a safe, effective and efficient manner. The present invention also seeks to provide a vaporising apparatus to convert a liquid fumigant to a gas or vapor suitable for application as a fumigant and to provide substantially homogenous dispersal or application of a fumigant into a treatment vessel. The present invention also seeks to provide a formulation, method and apparatus which substantially mitigates operational safety concerns in fumigation, including concerns relating to flammability of chemicals used in fumigation applications.

SUMMARY OF THE INVENTION

[0014] With the above objects in mind, according to a first aspect of the present invention there is provided a fumigant formulation comprising a quantity of liquid fumigant and an inert diluent, wherein the inert diluent is heated to a temperature above boiling point of liquid fumigant prior to introducing the inert diluent to the liquid fumigant, whereby contacting of the liquid fumigant with hot inert diluent increases temperature of the liquid fumigant sufficiently to form a vapour of liquid fumigant and inert diluent

[0015] Desirably, the liquid fumigant has one or more of insecticide, bactericide, herbicide and/or fungicide properties. Application of heat raises temperature of the liquid fumigant to above boiling point, creating a vaporised mixture of liquid fumigant and inert diluent which is suitable for application as a fumigant.

[0016] In a preferred embodiment, the liquid fumigant consists of one or more of methyl bromide, ethyl formate, methyl formate, methyl iodide, cyanogen, metham sodium, metham potassium, dimethyl sulphide, hydrogen cyanide, calcium cyanide, carbon dioxide, sulphur dioxide, carbon tetrachloride, ethylene dichloride, ethylene bromide, p-dichlorobenzene and γ-BHC.

[0017] In a preferred embodiment, the diluent is an inert gas, more preferably one or more of gaseous nitrogen (N₂), carbon dioxide (CO2) or Helium (He). Heating of the liquid fumigant is, in one embodiment, achieved by bubbling hot inert diluent through the liquid and heating the liquid to above its boiling point. The inert diluent advantageously acts as a carrier gas for the vaporised liquid fumigant. In a particularly preferred embodiment, the liquid fumigant is ethyl formate and the diluent is nitrogen gas. [0018] The liquid can be heated directly or indirectly. When heated directly, heat is applied to the liquid by an appropriate heating means, such as heating element or electric heater, located in or adjacent to the liquid. When the liquid is heated directly, the liquid is advantageously first contacted with inert diluent, to minimise oxygen levels in space around the liquid. When heated indirectly, the diluent is heated by appropriate heating means and the hot inert diluent is contacted with the liquid, thereby raising temperature of the liquid sufficiently to form vapour. Both approaches advantageously mitigate risk associated with flammability.

[0019] Advantageously, the fumigant formulation of the present invention provides a non-flammable vapour mixture that can be safely applied as a fumigant. The diluent can be supplied directly from an appropriate generator, such as a nitrogen generator or a container, e.g. a cylinder of gas. Combining of liquid and diluent is conveniently undertaken at the site requiring application of fumigant, allowing generation of non-flammable fumigant onsite where it can be directly applied to an area requiring treatment, such as a treatment container. Advantageously, this removes any need to handle and transport cylinderised gaseous fumigant

[0020] Liquid fumigant is advantageously vaporised in the vessel. In a preferred embodiment, liquid fumigant is vaporised in the vessel by bubbling hot inert gas into the liquid and/or into vessel headspace. The inert gas is introduced into the vessel at a temperature above the boiling point of the liquid fumigant. Heat from the hot inert gas transfers to the liquid fumigant, causing the liquid to vaporise in the vessel and forming a fumigant/inert gas mixture, whereby the inert gas acts as a carrier to the fumigant. Fumigant/inert gas is then directed to a treatment area or container for treatment, preferably at a temperature that ensures fumigant remains in a vaporised state.

[0021 ] This manner of vaporisation and application to the treatment area advantageously results in substantially homogenous application of fumigant/inert gas throughout the treatment area, providing effective fumigation and mitigating risk of damage to materials being treated.

[0022] According to a further aspect of the present invention, there is provided a vaporising apparatus for vaporising a liquid fumigant to enable application of the liquid as a fumigant, the apparatus comprising: a vessel to hold a quantity of the liquid fumigant, a source of diluent and a heating means, wherein the heating means heats diluent to a predetermined temperature and hot diluent is contacted with liquid fumigant in the vessel, whereby at least part of the liquid fumigant is vaporised, forming a liquid/diluent vapour; and an outlet through which vaporised liquid/diluent is expelled from the apparatus.

[0023] In one embodiment of the invention, the heating means is located in or adjacent the vessel to heat the liquid substantially directly. In this embodiment, the diluent is introduced into the vessel, preferably through the liquid, to purge the vessel, reducing the amount of oxygen in a headspace of the vessel.

[0024] In a second embodiment, the heating means is located to heat the diluent, whereby heated diluent is contacted with the liquid fumigant to raise temperature of the liquid sufficiently to form the vapour of liquid and diluent. In this embodiment, it is preferred that the heating means avoids direct contact with the liquid fumigant, thereby mitigating risk if the liquid fumigant is flammable.

[0025] The vessel is arranged to receive and hold a quantity of the liquid fumigant. In a preferred embodiment, the vessel has safety and/or measuring features to control the amount of liquid introduced into the vessel and to avoid spillage of the liquid fumigant. This is particularly useful if the liquid fumigant has properties that pose a safety risk, such as flammability and/or toxicity.

[0026] The diluent is desirably an inert gas and therefore the source of diluent may be provided by a generator, such as a pressure swing adsorption (PSA) or membrane separation (MS) and gas is generated as required before or during operation of the apparatus. Alternatively, the diluent source is provided in the form of a container for storing compressed gas, such as a cylinder.

[0027] The heating means is provided to heat the liquid fumigant to and above its boiling point, by direct or indirect heat transfer, and may take the form of any appropriate heating means, such as, but not limited to, an electric and/or heat exchange system. Desirably, the heating means is coupled with a control means to control heating temperature and maintain temperature at a level required to vaporise the liquid fumigant whilst the apparatus is in operation.

[0028] An input means directs diluent to the liquid fumigant whereby they are contacted to purge the vessel in the first embodiment and to heat the liquid fumigant and purge the vessel in the second embodiment. The apparatus additionally includes a mixing means to create turbulence when diluent is contacted with liquid fumigant. In a preferred embodiment, the mixing means includes a conduit, desirably having shape and configuration to create appropriate turbulence of liquid fumigant with diluent within the vessel to provide optimal mixing of liquid fumigant with the diluent. Flow of the diluent into the vessel via the mixing means is controlled at least in part via the control means, which may include electronic control of pressure regulators, valves and the like as appropriate.

[0029] For safety and operational control, the apparatus also includes at least one sensor. Desirably, the apparatus includes one or more temperature sensors. In a preferred embodiment, a first temperature sensor is located in or adjacent the vessel to monitor temperature of the liquid fumigant during operation of the apparatus. A second temperature sensor is arranged to monitor temperature of vaporised formulation at or near the outlet through which the vaporised formulation is expelled. The apparatus may also include other sensors as appropriate for operational and safety requirements, such as an oxygen sensor to monitor oxygen levels and ensure that oxygen levels are at levels sufficiently safe to mitigate risk of ignition of the liquid fumigant or its vaporised form; and/or a sensor that measures temperature of the diluent before it enters the vessel and/or temperature of vaporised diluent/fumigant as it exits the apparatus. Each of the sensors are preferably in communication with the control means so that operational parameters such as temperature and/or oxygen levels can be monitored and maintained at appropriate levels during operation of the apparatus.

[0030] Upon the liquid fumigant being warmed sufficiently to cause vaporisation, the combined vaporised liquid/diluent is expelled through the outlet and onto or into an area or volume requiring treatment, such as treatment container.

[0031 ] Advantageously, the arrangement of the apparatus enables the apparatus to be portable and allow onsite generation and application of vaporised formulation.

[0032] It is apparent that the fumigant formulation and apparatus of the present invention has utility in treating areas and/or quantities of a commodity by creation and application of a suitable fumigant. Thus, according to yet another aspect of the present invention, there is provided a method of treatment of a fumigant, the method including contacting a quantity of a liquid fumigant having one or more of insecticide, bactericide, herbicide and/or fungicide properties with an inert diluent and applying heat to raise temperature of the liquid fumigant sufficiently to form a vapour of liquid fumigant and inert diluent, whereby the vapour is applied to an area requiring treatment.

[0033] In a preferred embodiment, the method of treatment includes contacting a quantity of liquid fumigant with a hot, inert diluent, whereby heat from the inert diluent is transferred to the liquid fumigant to raise the temperature sufficiently to form a vapour of liquid fumigant and inert diluent. The resulting vapour consisting of fumigant with inert diluent as a carrier gas, is subsequently applied to an area or volume requiring treatment, such as treatment container. Desirably, the vaporised fumigant/diluent is introduced into the treatment area or container at a temperature that maintains the fumigant in a vaporised state.

[0034] The present invention finds particular utility in fumigation of foodstuffs, such as grain and fruit; as well as disinfestation of equipment, materials and facilities, including but not limited to linens, plastics and metals. The diluent serves as a carrier to apply appropriate pesticide, such as ethyl formate, into storage spaces, shipping containers and other sealed and semi-sealed chambers, buildings and structural spaces for purpose of controlling invertebrate pests. Advantageously, the present invention provides an eco-friendly replacement for known fumigants such as methyl bromide in a manner that mitigates known problems with alternative fumigants, such as flammability of ethyl formate. The present invention also advantageously provides insecticide, bactericide, herbicide and fungicide fumigation capacity efficiently and conveniently whilst simultaneously mitigating health and safety risks.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order for the present invention to be more readily understood, embodiments will now be described, by way of example, with reference to the accompanying drawings in which:

[0036] Figure 1 is a front and rear perspective view of a vaporising apparatus of the present invention;

[0037] Figure 2 is a front perspective view and front view of the vaporising apparatus of Figure 1 with outer housing removed;

[0038] Figure 3 is a side cross section of a vessel of a first embodiment of the apparatus; [0039] Figure 4 is a side cross section of a vessel of a second embodiment of the apparatus;

[0040] Figure 5 is a side cross section of the vessel of Figure 4 with an alternative mixing means;

[0041 ] Figure 6 is a perspective view of a further embodiment of a vessel of the apparatus;

[0042] Figure 7 is a cross-section view of the vessel of Figure 6;

[0043] Figure 8 is an exploded view of the vessel of Figure 6;

[0044] Figure 9 is a perspective view of a gas inlet and mixing means located in the vessel of Figure 6;

[0045] Figure 10 is a graphical representation of ethyl formate concentration applied to an empty 20 foot and 40 foot shipping container, recorded over a 6 hour exposure period; and

[0046] Figure 11 is a graphical representation of ethyl formate concentration over a period of 24 hours to observe decay of ethyl formate in a 20 foot and 40 foot loaded shipping container.

DESCRIPTION OF PREFERRED EMBODIMENT

[0047] Referring initially to Figures 1 and 2, there is shown a first embodiment of a vaporising apparatus 10 for use in vaporising a liquid fumigant 1 1 to enable application of the liquid fumigant 1 1 as a fumigant. Throughout this description, the invention will be described primarily in the context of the liquid fumigant 11 being ethyl formate. However, the present invention has equal applicability in utilisation of other liquid fumigants 1 1 including pesticides, herbicides, bactericides and/or fungicides. The present invention has particular utility in using liquid fumigants 1 1 having particular properties, including flammability, which would otherwise render the liquid unsuitable or undesirable for use as a fumigant.

[0048] The apparatus 10 includes a vessel 12 to receive and hold a quantity of liquid fumigant 1 1 , such as ethyl formate. One embodiment of the vessel 12 is shown in Figures 6 to 8. The vessel 12 can be provided in any suitable shape or configuration and is composed of material suitable, such as stainless steel, to safely retain a quantity of liquid fumigant 1 1 therein. The vessel 12 has an inlet 14, through which liquid fumigant 11 is introduced into the vessel 12 and an outlet 36 through which vaporised liquid fumigant 11 is expelled.

[0049] The inlet includes a filling port 14, which may incorporate a one way valve to enable the liquid to be introduced to the vessel 12 whilst avoiding spillage of liquid outwardly from the vessel 12. The filling port 14 is located in a lid 15 or top of the vessel 12. The filling port 14 additionally serves to ensure that the quantity of liquid fumigant 1 1 introduced into the vessel 12 is a quantity prescribed for the particular application at hand. The filling port 14 can include a dose specific dosing means. For example, fumigation treatment of a standard shipping container typically requires about 3L of liquid ethyl formate to be applied as a vapour and so in this instance, the filling port 14 would be operated to ensure that substantially 3L is introduced into the vessel 12. In the embodiment shown in the Figures, the filling port 14 has a cam-lock fitting or coupling to advantageously enable rapid connection and disconnection of a delivery pipe or hose, through which a predetermined quantity of liquid fumigant 1 1 can be pumped or otherwise delivered into the vessel 12.

[0050] The vessel 12 additionally has an outlet 28 disposed at the bottom of the vessel 12. The outlet 28 can be opened as required to discharge residues or dirty material from the vessel 12. In the embodiment shown in the Figures, the outlet 28 is provided as a lockable ball valve.

[0051 ] The apparatus 10 additionally includes a diluent source 16 which in a preferred embodiment is a source of an inert gas, including one or more of nitrogen (N₂), carbon dioxide (CO2) and helium (He). In one embodiment, the diluent can be provided in a container or tank suitable for storing compressed gas, such as a cylinder, which is arranged as a component of the apparatus 10. The cylinder should be of size that provides sufficient amount of diluent for at least one treatment application of the fumigant.

[0052] Alternatively, the diluent source 16 is a gas generator, able to generate sufficient quantity of inert gas as necessary. Non-limiting examples are pressure swing adsorption (PSA) or membrane separation (MS) nitrogen generators. In a preferred embodiment, the diluent source is a nitrogen generator capable of producing high quality (>99% nitrogen gas and further preferably >99.5% nitrogen gas). The nitrogen generator pumps dried, filtered and heated air though a bank of specially designed filtering membranes. These membranes separate the nitrogen from the CO₂ and O₂ exhaust gas and pass the nitrogen gas to a delivery pipe or other suitable conduit, for delivery to the vessel 12 of the apparatus 10.

[0053] The apparatus 10 additionally includes a heating means 18, which can be provided in an appropriate form, such as, but not limited to, an electric heater or heating element. The heating means 18 is arranged externally of the vessel 12 so that it does not directly provide heat to the vessel 12 or its contents. That is, heating of the liquid fumigant 1 1 is performed by indirect heating. This arrangement advantageously provides a high level of safety which mitigates risk, particularly if the liquid is flammable.

[0054] Diluent is directed to the heating means 18 from the diluent source via delivery pipe (not shown). At least one pressure regulator 44 and valve 46 is provided between the diluent source 16 and vessel 12 to assist in control of gas flow.

[0055] The heating means 18 operates to heat the diluent to a predetermined temperature. The diluent is warmed to a temperature that is dependent at least in part on the characteristics and/or chemistry of the liquid fumigant. It has been determined that when the liquid fumigant is ethyl formate, heater temperature and thus diluent temperature, should ideally not exceed 250°C. Upon heating the diluent, hot diluent is delivered into the vessel 12 to contact the liquid fumigant held therein, transferring heat thereto so as to heat the liquid to and above its boiling point, e.g. to above 54°C if the liquid is ethyl formate.

[0056] Hot diluent is introduced into the vessel 12 via inlet 20, which is typically a gas inlet. The inlet 20 is in fluid communication with a conduit 21 , located inside the vessel 12, such as shown in Figure 7. The conduit 21 extends substantially the length of the vessel 12 from the inlet 20 towards a lower portion of the vessel 12, where the conduit 21 continues as a coiled portion 24. The coiled portion 24 is immersed in liquid fumigant 1 1 once the liquid is introduced into the vessel 12.

[0057] The coil portion 24 has a series of apertures 48 arranged at substantially uniform intervals along a length thereof. The apertures 48 are each ideally micro-apertures, having total area of approximately 3mm². Apertures 48 may be located on an upper and/or lower surface of the coiled portion 24. The apertures 48 are arranged such that diluent can pass through the apertures 48 and into the liquid in the vessel 12.

[0058] In the embodiment shown in Figures 7 to 9, the coiled portion 24 spirals downwards to a bottom of the vessel 12 from an outermost coil towards the centre. The coiled portion 24 continues into a riser 26, which is in fluid communication with the coiled portion 24 and extends substantially vertically upwards inside the vessel 12. The riser 26 is also provided with one or more apertures 34 located at an uppermost portion of the riser 26. The apertures 34 are arranged in use, above the level of liquid fumigant 1 1 held within the vessel 12. That is, the apertures 34 are located in a headspace of the vessel 12.

[0059] The arrangement of apertures 48 in the coiled portion 24 advantageously creates turbulence of the liquid fumigant 1 1 as diluent enters the vessel 12 under pressure. This assists in distribution of the hot diluent throughout the vessel 12 to achieve substantially even contact with and heating of the liquid fumigant 1 1. Hot diluent also enters the vessel 12 via the riser apertures 34. Introduction of hot diluent into the vessel 12 at a level above the liquid fumigant 1 1 has the advantageous effect of preventing turbulence within the vessel 12 from becoming overly aggressive. It has been determined that if diluent is introduced into the vessel 12 solely below the level of liquid fumigant 1 1 , agitation in the vessel 12 can become too aggressive, decreasing the rate of vaporisation causing liquid fumigant 1 1 fluid to become entrained in the diluent flow and decreasing fumigant application time

[0060] The arrangement of the coiled portion 24 and apertures 48, as well as riser 26 and associated apertures 34 acts as a mixing means to ensure appropriate turbulence of liquid upon introduction of the diluent, as well as mixing of the vaporised fumigant with the hot diluent within the vessel 12 to create a substantially homogenous vapour. As hot diluent is passed through the coiled portion 24 and through the apertures 48, turbulence is created within the vessel, increasing evaporation rate of the liquid.

[0061 ] In the embodiment shown in Figure 5, there is shown an apparatus 10 having an alternative arrangement of inlet 20 for introducing diluent into the vessel 12. In this embodiment, instead of the coiled portion having a series of apertures, at least one vertical portion 22 extends upwardly into vessel 12. Each vertical portion 22 is provided with one or more apertures 48, through which diluent is delivered into the vessel 12 to contact the liquid and transfer heat so as to effect vaporisation of the liquid. As with previous embodiments, the total area of the apertures on the vertical portions 22 is about 3mm² or greater.

[0062] As an added safety measure, diluent is introduced into the vessel 12 before any heating of the diluent in order to purge air within the vessel 12 with diluent. As a safety measure, the heating means 18 is typically rendered as inoperable by a control means until the oxygen level within the vessel 12 is confirmed by an oxygen sensor to be below a predetermined level, typically 10% or less.

[0063] The vaporization apparatus 10 further includes a control means (not shown) which is in communication with the heating means 18, vessel 12 and gas inlet 20. The control means may take the form of a control box, connectable to the apparatus 10 via a pluggable cable. The control means is further in communication with at least one sensor to allow operation and/or adjustment of one or more operating parameters of the apparatus 10. The control means is ideally operable via a control panel, located on an exterior of the control box (not shown). The control box and panel is ideally segregated from the main body of the apparatus 10 and may include a sealed control box to protect interface components between the control panel and main body of the apparatus 10. The control means can be manipulated manually via the control panel and/or can be operated automatically via pre-programming such as with a programmable digital controller (PLC), pre-set with various parameters such as temperature, run time of the apparatus 10 and diluent flow rate.

[0064] The control means allows operation and adjustment of the heating means 18 to ensure that the diluent is heated to a temperature required to vaporise liquid fumigant 1 1 and maintain this temperature during operation of the apparatus 10. To this effect, the control means is in communication with at least one sensor, which includes at least one temperature sensor (not shown). A first temperature sensor is located in or adjacent the vessel 12 to monitor temperature of the liquid fumigant 1 1 as it is warmed and then vaporised. A second temperature sensor is located on or adjacent the heating means 18. Both temperature sensors are in communication with the control means. During operation, the control means is operated to raise the temperature of the heating means 18 to heat the diluent to a temperature sufficient to vaporise the liquid upon contacting the diluent with liquid. The temperature sensors provide temperature data feedback to the control means during operation of the apparatus so that temperature of the heating means 18 and contents of the vessel 12 are maintained at a level sufficient to maintain the liquid fumigant 1 1 in a vaporised state within the vessel 12 during operation of the apparatus 10.

[0065] Optionally, a third temperature sensor is located on or adjacent the outlet 36 to monitor temperature of the vapour as it is expelled from the apparatus 10. The third temperature sensor is similarly in communication with the control means and relays temperature data, in particular temperature of the liquid/diluent vapour to the control means so that the temperature of the heating means 18 can be adjusted if necessary, thereby ensuring that vapour exiting the apparatus 10 is sufficiently warm to remain in a vaporised state upon transfer to the area requiring treatment, typically a treatment container.

[0066] In addition to controlling temperature, the control means, which is in communication with gas pressure regulator 44 and valve 46 located along the gas inlet 20, also controls flow of diluent, including into the vessel 12 and of release of mixed vapour from the outlet 36. Flow of diluent can be controlled to purge components of the apparatus 10 prior to operation, in particular prior to heating by the heating means 18. The vessel 12 is purged with diluent prior to commencement of heating to substantially remove or reduce oxygen levels, thereby mitigating first of ignition of flammable compounds. Diluent can also be passed through to other components to purge of significant oxygen levels prior to commencement of heating.

[0067] One or more oxygen sensors (not shown) are provided to detect oxygen levels within various components of the apparatus 10, including the vessel 12, and communicate oxygen levels to the control means. The oxygen sensors provide added safety since the control means is programmed such that operation of the apparatus 10, in particular operation of the heating means 18, cannot be initiated and hence vaporisation of liquid will not occur unless oxygen levels are below safe levels in at-risk components of the apparatus 10. If oxygen levels are identified as being too high in any at-risk component of the apparatus 10, for example, above about 10%, power is prevented from being supplied at least to the heating means 18 and preferably to the apparatus 10 itself. It is particularly useful to monitor oxygen levels within the vessel 12 prior to commencement of heating so as to mitigate risk of ignition of any flammables, including the liquid held therein, as heat is applied.

[0068] One or more pressure sensors (not shown) can additionally be provided. Pressure sensor is located in the control box, whereby gas pressure in the control box is communicated to the control means and display screen. Pressure sensor monitors incoming diluent pressure and if diluent supply pressure drops below a predetermined level, the apparatus 10 is shut down via control means.

[0069] Once oxygen levels in at-risk components of the apparatus 10 are deemed to be sufficiently low and prescribed gas pressure in the control box has been achieved and this data communicated to the control means, operation of the vaporization apparatus 10 can commence. It is only once the oxygen sensor communicates sufficiently low levels of oxygen in the vessel 12 and control box, that power is connected to the apparatus to commence operation of the heating means 18 and apparatus 10. During operation of the apparatus 10, control means ensures that the control box is continually purged with diluent to mitigate ignition risk. Each of these functions are substantially automated, controlled by the control means and pre-programmed via suitable means such as PLC.

[0070] The heating means 18 thus acts to heat the diluent, whereupon the hot diluent is bubbled into and distributed through the liquid held in the vessel 12 via the apertures 48 and the turbulence created therefrom. On contacting the liquid with hot diluent, heat is transferred to the liquid from the hot diluent, vaporising the liquid within the vessel 12.

[0071 ] Once the liquid inside the vessel 12 has been heated sufficiently by the heating means 18 to vaporise substantially all of the liquid held therein, creating a mixture of fumigant/diluent vapour, the combined vapour can be expelled from the apparatus through the outlet 36 and into the area requiring treatment, such as into a 20 or 40 foot standard shipping container containing cargo requiring treatment.

[0072] The outlet 36 can be located on the lid 15 or top of the vessel 12, or in a side wall of the vessel 12. The outlet 36 includes a pipe or conduit (not shown), ideally a flexible tube, through which vaporised fumigant/diluent can be discharged outwardly of the apparatus 10 and to the area requiring fumigation.

[0073] The flexible tube (not shown) is connected to the outlet 36 via suitable means, such as a cam-lock connector. Ideally, the flexible tube is an anti-static flexible hose. The flexible tube channels vaporised fumigant/filuent mixture from the vessel 12 to the area requiring fumigation. An application nozzle can optionally be located at an end of the flexible tube distal to the apparatus 10 body.

[0074] The above described components of the apparatus 10, in particular the vessel 12 and heating means 18 are held in a housing 42 comprising frame 50 and cover 52, such that the vaporization apparatus 10 is presented as a substantially compact unit. The control panel is connectable through an exterior of the housing 42, such as by plugging into a compatible port. The housing 42 and components therein are mounted on a set of wheels to enable portability of the apparatus 10. Portability permits the apparatus to be readily moved from one treatment site to another by a single operator. [0075] In a preferred embodiment, the vaporization apparatus 10 is additionally provided with an emergency button or switch which is arranged to perform one or more of: cease diluent flow, disconnect power to the apparatus 10 and/or cease fumigant discharge. This feature is provided to further mitigate safety risk in the event of an emergency scenario.

Examples of Operation

Example 1: Operation of the Apparatus

[0076] Using the apparatus 10 of the present invention, a series of fumigation enclosures, in this case standard 20 and 40 foot general purpose shipping containers were treated with ethyl formate fumigant to treat for invertebrate pests.

[0077] A nitrogen generator as the diluent source, was placed locally to the fumigation area and switched on until approximately >99.4% nitrogen purity was achieved.

[0078] A measured quantity of ethyl formate was introduced into the vessel 12 through the filling port 14 via dose specific dosing container. This ensured that only the required measured amount of liquid ethyl formate required for this particular application was introduced into the vessel 12. A dose of 3L ethyl formate was provided for treating a 20 foot shipping container and a 6L dose for a 40 foot shipping container. Via operation of the control panel, inert and cool nitrogen gas was channelled from the gas generator into the vessel 12 and control box to purge atmosphere within these components.

[0079] Oxygen sensor and pressure sensor are programmed to take readings within at least the vessel 12 and control box (not shown), to prevent powering of the vaporization apparatus 10 and in particular the heating means 18, until prescribed levels of oxygen and pressure are achieved. In this case, power to the apparatus 10 were not switched on until the vessel 12 and control box had received about 99.4% nitrogen.

[0080] Upon nitrogen being purged into the control box and vessel 12, the oxygen sensor communicated low oxygen content in the vessel 12 to the control means. The pressure sensor in the control box also relayed gas pressure within the control box to the control means and control screen. This in turn allowed power to be automatically connected to the apparatus 10 and commence flow of nitrogen gas to the heating means 18. Nitrogen purging continued during operation of the vaporisation apparatus 10.

[0081 ] The heating means 18 operated to raise temperature of the nitrogen gas to about 180°. The heater temperature is monitored and controlled to not exceed 250°C during operation. Hot nitrogen gas was fed into the vessel 12 under pressure via the coiled conduit 24 to contact and mix with the liquid ethyl formate. Heat transfer from the hot gas caused vaporisation of substantially all of the liquid ethyl formate held inside the vessel 12. Upon the liquid fumigant 1 1 achieving vaporisation temperature, the continuing nitrogen carrier gas flow expelled both ethyl formate fumigant and nitrogen carrier gas outwardly of the apparatus 10 through the flexible tube (not shown) and into the fumigation chamber, i.e. into the 20/40 foot shipping container. Ethyl formate vapour at a concentration of about 90 g/m3 was delivered into the container, this being a concentration proven to effectively treat all invertebrate life stages.

[0082] The total available amount of ethyl formate was discharged into the shipping container within approximately seven minutes following commencement of vaporisation. Once all the ethyl formate in the vessel 12 was vaporised, the heater and gas flow was automatically shut down and the vessel 12 was dry. This signalled completion of the introduction of fumigant into the treatment container. The flexible delivery hose was then disconnected from the container and the apparatus 10. The treatment container was subsequently sealed for a holding period of six hours, whereupon all life stages of any invertebrates present within the container were observed to be killed.

[0083] During the holding period, the apparatus 10 was available to be moved to a neighbouring container requiring treatment, re-charged with an appropriate volume of liquid ethyl formate and the fumigation of the neighbouring container commenced substantially as described above.

[0084] At the end of the six hour fumigation period, a venting procedure was commenced, comprising opening of at least one door of the shipping container. Ventilation was continued until fumigant content in the head space of the container fell below the threshold limit value (TLV) of 100ppm. Once fumigant concentration fell to this level, the container was closed.

Example 2: Ethyl Formate Fumigation Trials - insect bioassays

[0085] The fumigation trials were conducted in 20 and 40 foot general purpose shipping containers. These containers were fitted with a network of gas sampling lines and structures for hanging insect bioassays. A total of 10 trials were conducted, initially focusing on the application and distribution of ethyl formate in empty containers. Gas monitoring points were located in all corners of the container and also in the centre of the container. After successful completion of these initial trials, a second set of trials were conducted which included placement of mock cargo items in the container to mimic typical cargo conditions. These second trials were conducted to (i) verify ethyl formate distribution to all parts of the container and cargo; and (ii) assess if items in the container had any effect on the absorption of ethyl formate.

[0086] Insect bioassays were carried out by placing three species of stored product insects at different locations throughout the container, which were subsequently examined to assess mortality. The insect species included: (i) rust red flour beetles {Tribolium castaneum); (ii) rice weevils {Sitophilus oryzae); and (iii) lesser grain borer {Rhyzopertha dominica). The bioassays consisted of mixed age cultures of these stored product insects. Following the ethyl formate exposure period, the insect cultures were counted on a weekly basis for 5 weeks. All alive and dead adults were removed after each count to observe any new emergence. Controls of each species were kept under similar conditions for comparative purposes. The bioassay assessment indicated complete control of all stages of T. castaneum and R. dominica. Some pupae survival of S. oryzae was observed.

[0087] Further trials were conducted to optimise dosage rate to ensure complete control of all stages of all species tested. It was determined that an initial dosage rate of approximately 90g/m³ ethyl formate over a period of 6 hours was sufficient for 100% control.

[0088] Gas concentration data gathered from the loaded containers were observed to be similar to those observed in the empty distribution trials. These results are shown in Figures 10 and 1 1.

[0089] After completion of fumigation, the container was naturally vented by opening the doors to permit natural ventilation. Observed increase in concentration of ethyl formate after this period was due to the desorption of ethyl formate vapour from the internal timber floor of the container overnight.

Example 3: Impact of Ethyl Formate + N₂ fumigation on drinks in metal and plastic containers

[0090] The following trials were undertaken to determine the impact of ethyl formate + N₂ fumigation on a range of products and to test for the presence of ethyl formate and its break down compounds (ethanol and formic acid) in the treated commodities after ethyl formate application. [0091 ] A 20 foot standard shipping container loaded with palletised drinks and food (cans of soft drink, plastic bottled water, breakfast cereals and milk powder) was fumigated using the inventive method and apparatus at a dosage rate of 90g/m³ ethyl formate. Standard application time for ethyl formate is 6 hours. In these trials, the container was treated for 28 hours to represent a worst case study. Ethyl formate, ethanol and formic acid were detected.

[0092] Samples of the different products were selected at random and analysed. The levels of ethyl formate, ethanol and formic acid were calculated on the basis of peak areas.

[0093] No residues of ethyl formate or break down compounds were detected (<LOD of 10ppb ethyl formate and ethanol; and <LOD 15ppb for formic acid) in any of the fumigated food or drink or unfumigated controls. These results are indicated in Table 1.

Table 1 : Ethyl forma e, ethanol and formic acid concentrations

^* levels detected in unfumigated samples represent natural background concentration in this food type Example 4: Impact of Ethyl Formate + N₂ fumigation on commodities/materials

[0094] This test was conducted to test the interaction between ethyl formate and materials exposed in the fumigation environment. The test measured ethyl formate residues in soft commodities and surface colour change of plastic and metal materials.

[0095] A fumigation chamber having total volume of 60L was constructed and fitted with a number of gas sampling ports. A range of commodities (see Tables 2 and 3) were placed into the chamber, these including a range of plastics, metals, electronic circuit boards, a computer, toilet paper, towels and bed sheets. The toilet paper, towels and bed sheets were wrapped in plastic packaging.

[0096] Toilet paper, towel and bed sheet wrapped in plastic packaging were placed into the container with a loading rate of 40% to represent standard work method statement for fumigation carried out with ethyl formate application of 90g/m₃ for 6 hours in a 20 foot container. At the end of the fumigation period, the container top was opened to vent ethyl formate for 2 hours.

[0097] Plastic and metal materials were placed in the container and ethyl formate + N₂ vapour was introduced into the container following vaporisation by the inventive apparatus and substantially as described above at fumigation conditions of 90 g/m³ dosage ethyl formate. At the end of the fumigation period, the container top was opened to vent ethyl formate for 0.5 hours. Fumigation was repeated two times.

[0098] The fumigated samples of paper, towel and bed sheet were selected at random and analysed for levels of ethyl formate, ethanol and formic acid. These results are shown in Table 2. No residues were detected. Commodity Fumigated (ppb, pg/kg ) Unfumigated (ppb, g/ kg)

EF ET FA EF ET FA

Toilet <10 <10 <15 <10 <10 <15 paper

Towel <10 <10 <15 <10 <10 <15

Bed sheet <10 <10 <15 <10 <10 <15

Table 2: Ethyl formate, ethanol and formic acid in soft commodities

[0099] There was no observable change in ethyl formate concentration in the headspace of the container containing plastic and metal materials, indicated there is no absorption of ethyl formate during fumigation. This in turn indicates there is no chemical reaction between tested plastic and metal materials and ethyl formate. Further, ethyl formate did not cause any corrosion on fumigated electronic circuit boards. The ethyl formate treated computer operated without any faults following fumigation. No surface colour change was detected on any of the tested plastics and metals, as outlined in Table 3.

Material After 1 day treatment After 10 day treatment

Mild steel No No

Aluminium grade 6061 No No

Copper No No

Acetal No No

Ultra high molecular No No

weight polyethylene

Polycarbonate No No

Aluminium No No

Brass No No

Acrylic No No

Nylon No No

Heatshrink tubing No No

(polyolefin)

Zinc No No

Polyurethane No No

Zinc plate No No

Powder coated steel No No

Extruded aluminium No No

(anodised)

Stainless steel (316-L) No No

High carbon steel 4140 No No

PVC No No Aluminium grade 4039 No No

Bronze No No

Silicone rubber No No

Table 3: observed colour change of materials treated by ethyl formate + N₂ fumigation

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A fumigant formulation comprising a quantity of liquid fumigant and a diluent, wherein the diluent is heated to a temperature above boiling point of liquid fumigant prior to introducing the diluent to the liquid fumigant, whereby contacting of the liquid fumigant with hot diluent increases temperature of the liquid fumigant sufficiently to form a vapour of liquid fumigant and diluent.

2. A fumigant formulation according to claim 1 , wherein the fumigant has one or more of insecticide, bactericide, herbicide and/or fungicide properties.

3. A fumigant formulation according to claim 1 or 2, wherein the diluent is an inert diluent.

4. A fumigant formulation according to any one of claims 1 to 3, wherein application of hot diluent raises temperature of the liquid fumigant to above boiling point, creating a vaporised mixture of liquid fumigant and diluent, suitable for application as a fumigant.

5. A fumigant formulation according to any one of the preceding claims, wherein the liquid fumigant consists of one or more of methyl bromide, ethyl formate, methyl formate, methyl iodide, cyanogen, metham sodium, metham potassium, dimethyl sulphide, hydrogen cyanide, calcium cyanide, carbon dioxide, sulphur dioxide, carbon tetrachloride, ethylene dichloride, ethylene bromide, p-dichlorobenzene and γ-BHC.

6. A fumigant formulation according to any one of the preceding claims, wherein the diluent is an inert gas.

7. A fumigant formulation according to claim 6, wherein the inert gas is one or more of gaseous nitrogen, carbon dioxide or helium.

8. A fumigant formulation according to any one of the preceding claims, wherein the liquid fumigant is heated by bubbling hot diluent through the liquid fumigant.

9. A fumigant formulation according to any one of the preceding claims, wherein the vapour of liquid fumigant and diluent comprises 20% or less liquid fumigant by volume in diluent.

10. A fumigant formulation according to claim 9, wherein the vapour of liquid fumigant and diluent comprises 10% or less liquid fumigant by volume in diluent

1 1. A vaporising apparatus for vaporising a liquid fumigant to enable application of the liquid as a fumigant, the apparatus comprising: a vessel to hold a quantity of the liquid fumigant, a diluent source and a heating means, wherein the heating means heats diluent to a predetermined temperature and hot diluent is contacted with liquid fumigant in the vessel, whereby at least part of the liquid fumigant is vaporised, forming a liquid/diluent vapour; and an outlet through which vaporised liquid/diluent is expelled.

12. A vaporising apparatus according to claim 1 1 , wherein the diluent source is in fluid communication with the heating means.

13. The vaporising apparatus according to claim 1 1 or 12, wherein diluent from the diluent source is introduced into the vessel to purge the vessel and reduce oxygen levels therein prior to heating.

14. A vaporising apparatus according to claim 13, wherein diluent is introduced into the vessel through the liquid fumigant.

15. A vaporising apparatus according to any one of claims 1 1 to 14, wherein the heating means is arranged to heat the diluent, whereby heated diluent is contacted with the liquid fumigant to raise temperature of the liquid sufficiently to form a vapour of liquid and diluent.

16. A vaporising apparatus according to any one of claims 1 1 to 15, wherein the heating means is arranged to avoid direct contact with the liquid fumigant.

17. A vaporising apparatus according to any one of claims 1 1 to 16, wherein the vessel has an inlet through which liquid fumigant is introduced into the vessel.

18. A vaporising apparatus according to any one of claims 1 1 to 17, wherein the diluent source is a container suitable for storing compressed gas.

19. A vaporising apparatus according to any one of claims 1 1 to 17, wherein the diluent source is a gas generator.

20. A vaporising apparatus according to claim 19, wherein the gas generator is one or more of pressure swing adsorption or membrane separation.

21. A vaporising apparatus according to any one of claims 1 1 to 20, wherein the heating means is one or more of electric heater, or heat exchange system.

22. A vaporising apparatus according to any one of claims 11 to 21 , further comprising a control means to control operational functions of the apparatus including the heating means.

23. A vaporising apparatus according to any one of claims 11 to 22, further comprising a mixing means to create turbulence when diluent is introduced into the vessel.

24. A vaporising apparatus according to claim 23, wherein the mixing means comprises a conduit located at least in part in the vessel and having one or more apertures to allow movement of diluent into the vessel, the conduit having shape and configuration adapted to create turbulence of liquid fumigant with diluent within the vessel upon introduction of diluent.

25. A vaporising apparatus according to claim 24, wherein diluent is introduced into the vessel under pressure.

26. A vaporising apparatus according to claim 24 or 25, wherein the one or more apertures are in use, located below a level of liquid fumigant in the vessel.

27. A vaporising apparatus according to any one of claims 24 to 26, wherein the mixing means further includes a riser having one or more apertures to allow passage of diluent into the vessel, the riser being arranged in the vessel such that the one or more apertures are in use, located in a headspace of the vessel.

28. A vaporising apparatus according to any one of claims 11 to 25, further comprising one or more sensors to sense one or more of temperature, oxygen level and/or gas pressure.

29. A vaporising apparatus according to claim 28, wherein said one or more sensors are in communication with control means to monitor, maintain and/or adjust operational parameters during operation of the apparatus.

30. A vaporising apparatus according to claim 28 or 29, wherein the control means is in communication with at least one oxygen sensor and operation of the heating means cannot be initiated until oxygen levels in at least the vessel are below a predetermined level.

31. A vaporising apparatus according to claim 28 or 29, wherein flow of diluent to heating means is initiated once oxygen levels in the vessel are below a predetermined level.

32. A method of treatment of an area requiring treatment with a fumigant, the method comprising heating a diluent to a predetermined temperature, contacting hot diluent with a quantity of a liquid fumigant having one or more of insecticide, bactericide, herbicide and/or fungicide properties, whereby heat from the hot diluent raises temperature of the liquid fumigant sufficiently to form a vapour of liquid fumigant and diluent, whereby the vapour/diluent mixture is applied to the area requiring treatment.

33. A method according to claim 31 , whereby the diluent is an inert gas.

34. A method according to claim 33, wherein the inert gas is nitrogen gas.

35. A method according to any one of claims 32 to 34, whereby the liquid fumigant is ethyl formate.

36. A method according to any one of claims 32 to 34, wherein the diluent is heated to a temperature above the boiling point of the liquid fumigant.

37. A method according to claim 36, wherein the diluent is heated to 150°C or above.

INNOVATIVE BIOSECURITY PTY LTD