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WO2002038467A1 - Insecticide / fongicide introduit dans une chambre a atmosphere controlee - Google Patents

Insecticide / fongicide introduit dans une chambre a atmosphere controlee Download PDF

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Publication number
WO2002038467A1
WO2002038467A1 PCT/AU2001/001431 AU0101431W WO0238467A1 WO 2002038467 A1 WO2002038467 A1 WO 2002038467A1 AU 0101431 W AU0101431 W AU 0101431W WO 0238467 A1 WO0238467 A1 WO 0238467A1
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WO
WIPO (PCT)
Prior art keywords
chamber
oxygen
atmosphere
substance
rate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/AU2001/001431
Other languages
English (en)
Inventor
Sanjay Savur
Richard Julian Spanier Aarons
Jordan A. Rodney
Leigh R. Barker
Lee J. Jones
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Australia Ltd
Original Assignee
Mitsubishi Australia Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Australia Ltd filed Critical Mitsubishi Australia Ltd
Priority to AU2002213671A priority Critical patent/AU2002213671A1/en
Publication of WO2002038467A1 publication Critical patent/WO2002038467A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVATION OF FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES; CHEMICAL RIPENING OF FRUIT OR VEGETABLES
    • A23B2/00—Preservation of foods or foodstuffs, in general
    • A23B2/70—Preservation of foods or foodstuffs, in general by treatment with chemicals
    • A23B2/704—Preservation of foods or foodstuffs, in general by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A23B2/708—Preservation of foods or foodstuffs, in general by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor in a controlled atmosphere, e.g. partial vacuum, comprising only CO2, N2, O2 or H2O
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVATION OF FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES; CHEMICAL RIPENING OF FRUIT OR VEGETABLES
    • A23B2/00—Preservation of foods or foodstuffs, in general
    • A23B2/70—Preservation of foods or foodstuffs, in general by treatment with chemicals
    • A23B2/704—Preservation of foods or foodstuffs, in general by treatment with chemicals in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVATION OF FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES; CHEMICAL RIPENING OF FRUIT OR VEGETABLES
    • A23B2/00—Preservation of foods or foodstuffs, in general
    • A23B2/70—Preservation of foods or foodstuffs, in general by treatment with chemicals
    • A23B2/725—Preservation of foods or foodstuffs, in general by treatment with chemicals in the form of liquids or solids
    • A23B2/729—Organic compounds; Microorganisms; Enzymes

Definitions

  • the invention relates to the field of introducing airborne substances such as insecticides or fungicides to a chamber.
  • One method of controlling the concentration of the substance is to actively monitor the concentration of the substance in the chamber atmosphere, and to vary the rate of release of the substance into the chamber based on the concentration measurements.
  • 20 depending upon the substance being introduced into the chamber it may not be possible to design a machine that is capable of accurately measuring the concentration of the substance in question.
  • the machinery required to do so is expensive.
  • a method for 30 introducing a substance into the atmosphere within a chamber and adjusting the chamber atmosphere such that the concentration of the substance does not substantially exceed a predetermined amount, the method comprising:
  • the input may be or include a gas mixture. It may be one or more distinct gas streams. It may be ambient air. It may be processed ambient air, such as by a splitter.
  • the concentration of the substance in the chamber atmosphere is maintained substantially at a predetermined constant concentration in the chamber atmosphere over an operative period following an equilibrating period.
  • the predetermined substance introduction rate has been calculated in accordance with a mathematical model of the proportions of chamber atmosphere constituents.
  • a preferred mathematical model is described below.
  • the present invention enables a substance to be introduced into the chamber atmosphere such that the concentration of the substance is maintained substantially at a predetermined constant concentration over an operative period in a cost effective manner that does not require any active monitoring or control of the concentration of the substance in the chamber atmosphere. Rather, all that is required is oxygen control in accordance with the invention.
  • a method for introducing a substance into the atmosphere within a chamber containing substantially non-respiring cargo such that the concentration of the substance in the chamber atmosphere is maintained substantially at a desired constant concentration in the chamber atmosphere over an operative period following an equilibrating period comprising:
  • the concentration of the substance in the chamber atmosphere is maintained substantially at a predetermined constant concentration in the chamber atmosphere over an operative period following an equilibrating period.
  • the predetermined substance introduction rate has been calculated in accordance with a mathematical model of the proportions of chamber atmosphere constituents.
  • a preferred mathematical model is described below.
  • a third aspect of the present invention there is provided a method for adjusting the atmosphere within a chamber to enable a cargo subject to degradation by insects to be stored with reduced degradation, the method comprising:
  • the insecticide may be carbon dioxide. Where the insecticide is carbon dioxide, the desired insecticidally effective concentration may be quite high, such as over 30% of the chamber atmosphere.
  • the method of the third aspect of the present invention may be applied to a chamber containing cargo which is further subject to degradation or deterioration through senescence, the method further comprising the step of, following the operative period, significantly reducing the rate of introduction of insecticide, or ceasing introduction of insecticide, and, optionally, varying the oxygen setpoint, to produce following an equilibrating period a predetermined chamber atmosphere composition, the predetermined composition being selected to delay or reduce further deterioration or further degradation of the cargo through senescence.
  • the atmospheric conditions for delaying further deterioration or further degradation of the cargo through senescence are preferably further selected so as to substantially limit further damage to the cargo by residual live insects.
  • the third aspect of the invention may be applied instead to a chamber with cargo subject to degradation by fungal growth to enable the cargo to be stored with reduced degradation, the reference to "insecticidally effective concentration” being replaced by “fungicidally effective concentration” and the reference to “killing a substantial proportion of the insects” being replaced by a reference to “killing a substantial proportion of the fungal growth”.
  • a method for introducing two or more substances into the atmosphere within a chamber such that the concentrations of the substances in the chamber atmosphere are maintained substantially at respective desired constant concentrations in the chamber atmosphere over an operative period following an equilibrating period comprising:
  • the concentrations of the substances in the chamber atmosphere are preferably maintained substantially at respective predetermined constant concentrations in the chamber atmosphere over an operative period following an equilibrating period.
  • the predetermined substance introduction rates have been calculated in accordance with a mathematical model of the proportions of chamber atmosphere constituents.
  • a method for introducing a substance into the atmosphere within a chamber such that the concentration of the substance within the chamber atmosphere does not substantially exceed a predetermined amount comprising introducing the substance into the chamber at one or more predetermined substantially constant rates during one or more periods of time, the predetermined rate or rates having been selected such that the concentration of the substance within the chamber atmosphere does not substantially exceed the predetermined amount.
  • the rate or rates are selected according to the methods described herein.
  • a method for introducing a substance into the atmosphere within a chamber containing respiring produce and for adjusting the chamber atmosphere such that the concentration of the substance does not substantially exceed a predetermined amount comprising maintaining the oxygen concentration substantially at a predetermined oxygen setpoint according to one of the oxygen concentration control methods described herein.
  • oxygen concentration control methods are described in detail below.
  • these methods provide for the oxygen concentration to be maintained substantially at a predetermined setpoint by admitting, or causing to be admitted, an oxygen containing gas (such as ambient atmosphere which contains approximately 21% oxygen by volume) into the chamber when the oxygen concentration falls below the setpoint (or below a point within a suitable margin or tolerance about the setpoint), and causing or permitting chamber atmosphere to exit the chamber.
  • an oxygen containing gas such as ambient atmosphere which contains approximately 21% oxygen by volume
  • the amount of chamber atmosphere exiting the chamber will be approximately the same amount or volume of chamber atmosphere as admitted to the chamber.
  • the above methods for introducing a substance into a chamber atmosphere enable substances which should not exceed the predetermined amount, to be introduced into the chamber without any need for active monitoring of the concentration of the substance in the chamber atmosphere.
  • the substance may be an insecticide.
  • the substance may be a fungicide. It may be a fumigant. It may be a bactericide.
  • the substance according to the invention may be a mixture of substances.
  • the substance may be moisture (ie. water) to provide humidif ⁇ cation.
  • the method may maintain humidity in a chamber containing respiring produce.
  • the method may take into account the contribution to the moisture level in the chamber atmosphere made by moisture generated by respiration.
  • the method may take into account the contribution to the moisture level in the chamber atmosphere made by moisture in the ambient atmosphere.
  • the methods may further comprise the step of removing carbon dioxide substantially at a predetermined rate, the predetermined rate having been selected such that the carbon dioxide concentration within the chamber atmosphere will not substantially exceed a predetermined amount.
  • apparatus for introducing a substance into the atmosphere within a chamber containing respiring produce and for adjusting the chamber atmosphere such that the concentration of the substance does not substantially exceed a predetermined amount, the apparatus comprising:
  • sealing means for sealing the chamber to the extent required to effect oxygen concentration control according to one of the oxygen concentration control methods described herein;
  • a controller having an oxygen concentration sensor and control means responsive to the oxygen concentration sensor, the control means being adapted to cause the inlet means and/or the oudet means, as applicable, to open to admit, or to cause to be admitted, ambient atmosphere into the chamber following the oxygen concentration sensor detecting that the oxygen concentration in the chamber has fallen below a predetermined amount;
  • substance introduction means for introducing the substance into the chamber atmosphere at one or more predetermined substantially constant rates during one or more respective periods of time so that the concentration of the substance does not substantially exceed the predetermined amount.
  • apparatus for introducing a substance into the atmosphere within a chamber and adjusting the chamber atmosphere such that the concentration of the substance does not substantially exceed a predetermined amount, the apparatus comprising:
  • a controller having an oxygen concentration sensor and control means responsive to the oxygen concentration sensor, the control means being adapted to cause to be admitted into the chamber an input containing oxygen following the oxygen concentration sensor detecting that the oxygen concentration in the chamber has fallen below a predetermined oxygen setpoint;
  • substance introduction means for introducing the substance into the chamber atmosphere at one or more predetermined substantially constant rates during one or more respective periods of time so that the concentration of the substance does not substantially exceed the predetermined amount.
  • apparatus for introducing a substance into the atmosphere within a chamber and adjusting the chamber atmosphere such that the concentration of the substance does not substantially exceed a predetermined amount, the apparatus comprising:
  • a controller having an oxygen concentration sensor for measuring the oxygen concentration in the chamber atmosphere and control means responsive to the oxygen concentration sensor, the control means being adapted to control the substance introduction means to vary the substance introduction rate in dependence on the measured oxygen concentration in the chamber so that the concentration of the substance does not substantially exceed the predetermined amount.
  • These apparatus may further comprise carbon dioxide reduction means to remove carbon dioxide from the chamber atmosphere at a predetermined rate so that the carbon dioxide concentration within the chamber atmosphere will not substantially exceed a predetermined amount.
  • a method for converting a receptacle into an adjusted atmosphere chamber containing respiring produce comprising:
  • a method for converting a receptacle into an adjusted atmosphere chamber arranged such that a substance is introducible into the chamber atmosphere such that the concentration of the substance will not substantially exceed a predetermined amount comprising:
  • a method for converting a receptacle into an adjusted atmosphere chamber wherein a substance is introducible into the chamber atmosphere such that the concentration of the substance will not substantially exceed a predetermined amount comprising: (a) forming a chamber in the receptacle optionally including installing sealing means to seal the chamber to the desired extent;
  • a receptacle when converted into an adjusted atmosphere chamber in accordance with the methods for converting a receptacle into an adjusted atmosphere chamber described herein.
  • the oxygen concentration control according to the invention may be achieved in any suitable way.
  • the chamber is substantially sealed (if necessary by applying appropriate sealing means to the chamber) and is provided with openable and closeable inlet and outlet means to, respectively, enable oxygen containing gas (such as ambient atmosphere) to enter the chamber and chamber atmosphere to exit the chamber.
  • oxygen containing gas such as ambient atmosphere
  • the inlet and oudet means may be opened for a suitable length of time following detection that the oxygen concentration has fallen below the setpoint (or below a point within a suitable margin or tolerance about the setpoint) .
  • ambient atmosphere is the oxygen containing gas
  • ambient atmosphere may be drawn or forced into the chamber by placing the inlet means near a source of low pressure within the chamber, and/or near a source of high pressure outside the chamber.
  • opening of the outlet means will result in chamber atmosphere being forced or drawn out from the chamber as a result of the slight increase in pressure of the chamber atmosphere following entry of the ambient atmosphere into the chamber (assuming, of course, that the outlet means is not placed near a source of low pressure within the chamber, or a source of high pressure outside the chamber) .
  • chamber atmosphere may be drawn or forced out of the chamber by placing the outlet means near a source of high pressure within the chamber, and/or near a source of low pressure outside the chamber.
  • opening of the inlet means will result in chamber atmosphere being drawn into the chamber as a result of the slight decrease in pressure of the chamber atmosphere following the exit of chamber atmosphere from the chamber (assuming, of course, that the inlet means is not placed near a source of high pressure within the chamber, or a source of low pressure outside the chamber).
  • the inlet means is opened for a time that is approximately proportional to the difference between the detected oxygen concentration and the oxygen setpoint.
  • the oxygen control is effected by, following detection that the oxygen concentration in the chamber has fallen below the relevant predetermined amount, causing chamber atmosphere to exit the chamber through an opening so that the pressure in the chamber is or will be reduced below ambient pressure such that ambient atmosphere is or will be drawn into the chamber through an opening so that the amount of oxygen in the chamber increases.
  • the chamber must be sealed to the extent that when the pressure within the chamber is substantially equal to ambient pressure the rate of leakage of oxygen into the chamber is less than the rate of consumption of oxygen by the respiring produce, and it must be open to the extent that when the chamber pressure is less than ambient pressure as described, the rate of entry of oxygen into the chamber is greater than the rate of consumption of oxygen by the respiring produce.
  • the opening to permit ambient atmosphere to enter the chamber may be the same opening as the opening to permit chamber atmosphere to exit the chamber.
  • a distinct opening is provided in the form of an openable and closeable outlet means to permit chamber atmosphere to exit the chamber.
  • Chamber atmosphere may be caused to exit the chamber through an opening by locating the opening near a source of high pressure inside the chamber, such that chamber atmosphere is expelled from the chamber through the opening.
  • the source of high pressure may be supplied by a fan.
  • the refrigeration fan may be used as a source of high pressure.
  • Chamber atmosphere may be caused to exit the chamber through an opening by locating the opening near a source of low pressure outside the chamber, such that chamber atmosphere is drawn out of the chamber through the opening.
  • the source of low pressure may be supplied by a fan.
  • An opening for permitting ambient atmosphere to enter the chamber may be provided wholly or partly by leakage paths into the chamber.
  • An opening may be added to the chamber, such as by making one or more holes in the chamber.
  • An opening may comprise existing leakage paths into the chamber.
  • ambient atmosphere may be drawn into the chamber through the opening following turning off the source of high or low pressure (as the case may be), or removing it from the vicinity of the opening, so that when the pressure in the chamber is below ambient pressure, ambient atmosphere may be drawn into the chamber through the opening.
  • the outlet means is preferably opened for a time that is approximately proportional to the difference between the detected oxygen concentration and the oxygen setpoint. Chamber not substantially sealed - initial pressure increase
  • the oxygen control is effected by, following detection that the oxygen concentration in the chamber has fallen below the relevant predetermined amount, causing ambient atmosphere to enter the chamber through an opening so that the amount of oxygen in the chamber increases and so that the pressure in the chamber exceeds ambient pressure such that chamber atmosphere is expelled from the chamber through an opening.
  • the chamber must be sealed to the extent that when the pressure within the chamber is substantially equal to ambient pressure the rate of leakage of oxygen into the chamber is less than the rate of consumption of oxygen by the respiring produce, and it must be open to the extent that when the chamber pressure is greater than ambient pressure as described, the rate of leakage of chamber atmosphere out of the chamber is sufficient to reduce the chamber pressure, before the oxygen concentration in the chamber again falls below the predetermined amount, to a level that will not prevent ambient atmosphere from entering the chamber through the opening first referred to above.
  • the opening to permit ambient atmosphere to enter the chamber may be the same opening as the opening to permit chamber atmosphere to exit the chamber.
  • a distinct opening is provided in the form of an openable and closeable inlet means to permit chamber atmosphere to enter the chamber.
  • Chamber atmosphere may be caused to enter the chamber through an opening by locating the opening near a source of low pressure inside the chamber, such that chamber atmosphere is drawn into the chamber through the opening.
  • the source of low pressure may be supplied by a fan.
  • the refrigeration fan may be used as a source of low pressure.
  • Chamber atmosphere may be caused to enter the chamber through an opening by locating the opening near a source of high pressure outside the chamber, such that chamber atmosphere is forced into the chamber through the opening.
  • the source of high pressure may be supplied by a fan.
  • An opening for permitting chamber ambient atmosphere to exit the chamber may be provided wholly or partly by leakage paths into the chamber.
  • An opening may be added to the chamber, such as by making one or more holes in the chamber.
  • An opening may comprise existing leakage paths into the chamber.
  • ambient atmosphere may be caused to enter the chamber through the opening following turning off the source of high or low pressure (as the case may be), or removing it from the vicinity of the opening, so that when the pressure in the chamber is above ambient pressure, chamber atmosphere may be forced out of the chamber through the opening.
  • the inlet means is preferably opened for a time that is approximately proportional to the difference between the detected oxygen concentration and the oxygen setpoint.
  • General chamber Oxygen control can be effected in a general chamber, not necessarily substantially sealed, or partially sealed in the manner described above.
  • the general oxygen control method used in conjunction with the present invention is as follows:
  • This method may be implemented using apparatus according to the present invention.
  • This general method of oxygen control provides two significant advantages in connection with introducing a substance into the chamber atmosphere such that the concentration of the substance does not substantially exceed the predetermined amount.
  • the requirement of substantial sealing or partial sealing of the chamber as discussed above means that many containers cannot be immediately employed as modified atmosphere containers. Such containers must in many cases be rejected altogether, or be repaired to reduce the degree of leakage to a suitable level to enable the containers to be used.
  • the inventors have realised that a chamber which is open to a greater degree than the partial sealing discussed above can be employed together with a chamber containing respiring produce by adding an oxygen load to the chamber to take up oxygen at a rate which is greater than the net rate of leakage of oxygen into the chamber less the rate of consumption of oxygen by the respiring produce at the setpoint, so that after an equilibration period, the oxygen concentration within the chamber atmosphere is maintained substantially at the setpoint.
  • This method enables many containers that would be too leaky to be employed in previously developed atmosphere adjustment methods to be immediately employed in the present method as a modified atmosphere container without any need for repair to reduce the degree of leakage, and without any need to have ongoing chamber atmosphere purging with a gas of low oxygen concentration.
  • the method of the first embodiment of the invention may be applied to a chamber containing respiring produce, the chamber being open to the extent that the net rate of leakage of oxygen into the chamber from the ambient atmosphere is greater than the rate of consumption of oxygen by the respiring produce, wherein the oxygen containing input is provided by ambient air, and wherein the oxygen removal is effected in part by the respiring produce and in part by removing oxygen from the chamber atmosphere substantially at a predetermined oxygen removal rate, the predetermined oxygen removal rate being greater than the net rate of leakage of oxygen into the chamber less the rate of consumption of oxygen by the respiring produce at the setpoint.
  • the rate of consumption of oxygen by the respiring produce at the setpoint may be estimated by known methods from a knowledge of relevant data, such as the type of produce, the mass of the produce and the storage temperature. If the carbon dioxide level within the chamber atmosphere is to be adjusted as detailed below, then the maximum desired carbon dioxide level may also be taken into consideration when estimating the rate of consumption of oxygen by the respiring produce at the setpoint.
  • Any suitable method of estimating the net rate of leakage of oxygen into the chamber may be used, together with the estimate of the rate of consumption of oxygen by the respiring produce, as a basis for selecting the predetermined oxygen removal rate.
  • One method is to employ the principle that, at a constant pressure within the container, the flow rate into the container must equal the flow rate out of the container (through the various leakage paths) . Accordingly, air may be pumped into the container at a known flow rate until the pressure remains constant at a particular target pressure (for example, 150 pascals above atmospheric pressure).
  • the resultant flow rate represents a maximum flow rate that could occur in practice by leakage through diffusion and/or convection.
  • the pressure is substantially uniform throughout the chamber, whereas, in practice, pressure gradients will be present throughout the chamber so that a pressure difference of, say, 150 Pa, will only exist in the vicinity of a fan in the chamber.
  • an estimate of the likely maximum or upper limit of the net rate of leakage of oxygen into the chamber may be made by taking 21% of the measured leakage rate at the target pressure, since oxygen makes up approximately 21% by volume of ambient air. Accordingly, if the predetermined oxygen removal rate is chosen to equal or exceed this maximum measure of oxygen leakage into the chamber, less the rate of oxygen consumption by the respiring produce, then the predetermined oxygen removal rate will exceed the amount required by the present invention.
  • the principle underlying this aspect of the present invention is as follows. In principle, and assuming the oxygen level in the chamber atmosphere has reached the oxygen setpoint, if oxygen were to be removed from the chamber atmosphere at a rate precisely equal to the difference between the net rate of leakage of oxygen into the chamber and the rate of consumption of oxygen by the respiring produce (being the respiration rate for the produce in question at the particular oxygen setpoint) , then the oxygen concentration within the chamber would remain at the setpoint.
  • the invention requires oxygen to be removed from the chamber atmosphere at a greater rate. Accordingly, but for the admission of oxygen by the active oxygen monitoring and control, there would be insufficient oxygen in the chamber to meet the respiration requirement of the respiring produce (at the particular oxygen setpoint) . The requirement that sufficient oxygen is removed to require oxygen admission ensures that the active monitoring and control of oxygen level causes the oxygen level to be maintained substantially at the oxygen setpoint.
  • the second advantage of the general oxygen control method is that it allows a substance to be introduced into the chamber such that it will not exceed a given concentration where respiring produce does not constitute the cargo.
  • This has considerable advantage in enabling the method to be applied to the storage of substantially non-respiring cargo such as meat and grain which may nevertheless benefit from storage or transportation under modified atmosphere conditions to delay deterioration or degradation through senescence, or where a fungicide, insecticide or other fumigant is required to prevent or reduce a particular means of deterioration or degradation of the cargo in circumstances where it is not practical to actively measure and control the fumigant concentration.
  • the oxygen load may be any suitable means for removing oxygen from the chamber atmosphere.
  • at least part of the oxygen removal is effected by contacting a quantity of oxygen absorbing material with the chamber atmosphere.
  • the oxygen absorbing material may be any suitable material for absorbing oxygen.
  • Oxygen absorbing materials known from the field of packaging of foods may be suitable for use in the present invention.
  • one class of oxygen absorbing materials suitable for use with the invention includes finely divided iron powder which takes up oxygen in an oxidation reaction (ie. the iron rusts).
  • Another class of oxygen absorbing materials suitable for use with the invention contains ascorbic acid. Materials of these classes are sold under the trade name Ageless, marketed by Mitsubishi Gas Chemical Co.
  • the oxygen absorbing material is preferably contained in at least one oxygen transmissible container, such as for example an oxygen transmissible bag.
  • the at least one oxygen transmissible container is selected so that the rate of oxygen transmission into the at least one oxygen transmissible container is substantially equal to the predetermined oxygen removal rate.
  • this information may be used to calculate the oxygen transmissibility properties of one or more containers of oxygen absorbing material.
  • k 0 represents the flow rate of oxygen through the film (typically in litres per minute), per percent of oxygen in the atmosphere, per unit area of film (typically in square metres) .
  • a 0 suitable flow units
  • Suitable oxygen transmissible containers may then
  • Po 2 be selected based on the product k 0 A .
  • the oxygen load may include an artificial respiration load, that is an oxygen load which consumes oxygen and produces carbon dioxide.
  • the oxygen removal and carbon dioxide introduction may both be effected by an artificial respiration load.
  • the artificial respiration load may be provided by effecting a chemical reaction that consumes oxygen and produces carbon dioxide.
  • the chemical reaction may produce carbon dioxide at a greater or lesser molar rate than the rate at which oxygen is consumed.
  • a substance which consumes oxygen and produces carbon dioxide is a mixture of iron carbonate and ascorbic acid.
  • the artificial respiration load may be provided by fermentation.
  • the artificial respiration load may be provided by combustion. It may be provided by a photosynthetic substance. It may be provided by a biochemical reaction.
  • the biochemical reaction may be an enzymatic reaction.
  • the length of time for which the oxygen containing input is admitted (such as by opening an inlet means) and/or the length of time for which chamber atmosphere is caused or permitted to exit the chamber (such as by opening an outlet means) may suitably be approximately proportional to the difference between the measured oxygen concentration and the oxygen setpoint.
  • approximately proportional we mean that the length of time the inlet means or outlet means is open should be small if the difference is small and large if the difference is large.
  • a true proportionality in the sense of a linear relationship between oxygen concentration difference and length of time of opening of the inlet means or outlet means is not required. (This situation only arises when the measured oxygen concentration is less than the oxygen setpoint because when the measured oxygen concentration exceeds the oxygen setpoint, the inlet means and/or outlet means would remain closed.)
  • logic of the following form is used to control the oxygen concentration within the chamber (in this embodiment ambient air is used as the oxygen containing input) :
  • Measurement of chamber oxygen concentration takes place at predetermined constant intervals, for example every 8 minutes.
  • an inlet means is opened to allow ambient air to enter the chamber to thereby increase the oxygen concentration within the chamber.
  • the inlet means and/or outlet means is/are closed after the measured oxygen concentration has exceeded the oxygen setpoint.
  • the inlet means and/or outlet means is/are opened to allow ambient air to enter the chamber to thereby increase the oxygen concentration within the chamber.
  • the inlet means and/or outlet means is/are closed after a time dependent on the oxygen concentration as measured prior to opening the inlet means.
  • the dependence on the oxygen concentration as measured takes the following form:
  • the chamber may be flushed with a gas having a low oxygen concentration or containing no oxygen. Nitrogen may be used as the gas. Such a gas flushing step may be effected to lower the initial oxygen concentration within the chamber to below a predetermined maximum oxygen concentration. If the oxygen content is thereby lowered below a predetermined minimum oxygen concentration, the controller may operate to cause the oxygen concentration within the chamber to be increased. If such a gas flushing step were not carried out, it could take considerable time for the oxygen concentration within the chamber to be lowered as a result of the removal of oxygen, such as by the consumption of oxygen by produce during respiration.
  • the gas flushing step would typically occur after produce has been loaded into a chamber fitted with atmosphere adjustment apparatus according to the present invention.
  • the gas flushing step is preferably used to lower the initial oxygen concentration the chamber to within a few percent of the oxygen setpoint.
  • the gas flushing step may be used to control the initial carbon dioxide concentration in the chamber atmosphere.
  • the gas flushing step may in theory be carried out in conjunction with any of the oxygen concentration control methods described herein. However, typically, one would only expect to go to the trouble and expense of carrying out a gas flushing step where a substantially sealed chamber is used (and where oxygen concentration control is accordingly based on the use of a substantially sealed chamber) .
  • the methods and apparatus of the invention may be adapted to operate based on active measurement and control of a principal chamber atmosphere constituent other than oxygen, provided that the concentration of the constituent in the chamber atmosphere can be readily measured.
  • a method for introducing a substance into the atmosphere within a chamber and adjusting the chamber atmosphere such that the concentration of the substance does not substantially exceed a predetermined amount comprising:
  • the principal chamber atmosphere constituent subject to being maintained substantially at the setpoint could be carbon dioxide. Any suitable chamber atmosphere constituent may be used.
  • the predetermined introduction rate of the substance into the chamber atmosphere may be calculated from a formula derived from a mathematical model of the proportions of chamber atmosphere constituents.
  • the mathematical model may be a continuous flow model. That is, notwithstanding that the flow of oxygen containing gas into the chamber, and of chamber atmosphere out of the chamber, may not be continuous flow, nevertheless, for the purpose of calculation, the flow of ambient atmosphere into the chamber, and of chamber atmosphere out of the chamber, may be modelled as being continuous flow.
  • a model may be based on discrete time intervals rather than using the continuous flow approximation.
  • the substance introduction rate is preferably calculated from a formula that produces a result substantially equal to the result produced by a calculation in accordance with the following formula:
  • R s is the substance introduction rate
  • a s is the rate of removal of the substance from the chamber atmosphere (for avoidance of any doubt not including removal from the chamber by chamber atmosphere exiting the chamber); a 0 is the rate of oxygen gas removal from the chamber atmosphere (for avoidance of any doubt not including removal from the chamber by chamber atmosphere exiting the chamber) ;
  • X t 0 is the proportion of oxygen gas in the input divided by the proportion of the further constituent in the input;
  • p 0 is the oxygen setpoint expressed as a proportion
  • p s is the predetermined concentration of the substance, expressed as a proportion
  • ⁇ is the sum of the concentrations of any further principal chamber atmosphere constituents, expressed as proportions.
  • Equation (1) is expressed in general form and accordingly some of these quantities may be zero. For example, if the oxygen containing input includes an inert gas which is not absorbed or adsorbed from the chamber atmosphere, and is not otherwise consumed or broken down in the chamber, then a ⁇ will be zero.
  • r Q is the respiration rate of produce in the chamber
  • p co is the equilibrium carbon dioxide concentration
  • a suitable model of the rate of removal of the substance from the chamber atmosphere will be absorption or adsorption of the substance from the chamber atmosphere at a rate proportional to the concentration of the substance in the chamber atmosphere.
  • the substance may be absorbed or adsorbed into or onto the chamber walls and/or objects within the chamber, such as the cargo.
  • a s may be modelled by a formula that produces a result substantially equal to the result produced by a calculation in accordance with the following formula:
  • the constant of proportionality k s may be calculated as follows:
  • k t and -4 represent, respectively, constants of proportionality and areas of different surface types of the boundary and of objects within the chamber.
  • the substance introduction rate may be calculated from a formula that produces a result substantially equal to the result produced by a calculation in accordance with the following formulae:
  • R. and R are the substance introduction rates; a, and a. are the rates of removal of the substances from the chamber atmosphere;
  • a 0 is the rate of oxygen gas removal from the chamber atmosphere
  • a t is the rate of removal from the chamber atmosphere of a further constituent of the gas stream not being oxygen gas
  • X t 0 is the proportion of the further constituent in the gas stream divided by the proportion of oxygen gas in the gas stream;
  • p 0 is the oxygen setpoint expressed as a proportion
  • ⁇ is the sum of the concentrations of any further principal chamber atmosphere constituents, expressed as proportions.
  • the substance introduction means comprises a storage for the substance and one or more associated atomisers for introducing the substance into the chamber atmosphere as a fine mist or spray.
  • the introduced substance may be a liquid. It may be a gas.
  • the substance may be provided by being dissolved in a suitable solvent.
  • the substance may be, or be dissolved in, a volatile liquid, and be introduced by vaporisation.
  • the method of the first aspect of the present invention in which the substance is independently introduced into the chamber atmosphere, may be applied to a chamber containing respiring produce.
  • carbon dioxide will be a principal chamber atmosphere constituent.
  • the method may further comprise removing carbon dioxide from the chamber atmosphere substantially at a predetermined carbon dioxide removal rate, the predetermined carbon dioxide removal rate having been selected such that the carbon dioxide concentration within the chamber atmosphere does not substantially exceed a predetermined amount lower than the carbon dioxide concentration which would result if no carbon dioxide removal was effected.
  • the predetermined substance introduction rate and the predetermined carbon dioxide removal rate may be calculated in accordance with a mathematical model of the proportions of chamber atmosphere constituents.
  • the substance introduction rate and the carbon dioxide removal rate are calculated from formulae that produce results substantially equal to the results produced by calculations in accordance with the following formulae:
  • R. is the substance introduction rate
  • a s is the rate of removal of the substance from the chamber atmosphere
  • a 0 is the rate of oxygen gas removal from the chamber atmosphere
  • ⁇ is the rate of removal from the chamber atmosphere of a further constituent of the input not being oxygen gas
  • X l 0 is the proportion of the further constituent in the input divided by the proportion of oxygen gas in the input;
  • p 0 is the oxygen setpoint expressed as a proportion
  • p s is the predetermined concentration of the substance, expressed as a proportion
  • a co is the rate of carbon dioxide removal from the chamber atmosphere
  • p co is the carbon dioxide concentration in the chamber atmosphere expressed as a proportion
  • the equilibrium carbon dioxide concentration may be calculated from a formula that produces a result substantially equal to the result produced by a calculation in accordance with the following formula:
  • r 0 is the rate of oxygen consumption through respiration and r co is the rate of production of carbon dioxide through respiration (whether normalised or in suitable units) .
  • the equilibrium carbon dioxide concentration may be allowed to result simply from the maintenance of the oxygen concentration within the chamber substantially at the setpoint without any steps being taken to control the carbon dioxide concentration. However, if it is desired to modify the equilibrium carbon dioxide concentration which would result if no modification were undertaken, then the carbon dioxide concentration may be adjusted by active carbon dioxide adjustment or passive carbon dioxide adjustment.
  • the carbon dioxide concentration may be passively adjusted by removing carbon dioxide from the chamber substantially at a predetermined rate.
  • the predetermined carbon dioxide removal rate is preferably calculated from a formula that produces a result substantially equal to the result produced by a calculation in accordance with the following formula:
  • this information may be used to calculate the carbon dioxide transmissibility properties of one or more containers of carbon dioxide absorbing material, such as bags of lime.
  • Suitable carbon dioxide transmissible containers may then be selected based on the product kco 2 A ⁇
  • the predicted equilibrium carbon dioxide concentration in the chamber can be set in advance so that it will reach the desired level by using a carbon dioxide concentration reduction means (such as carbon dioxide transmissible containers filled with carbon dioxide absorbing material) .
  • a carbon dioxide concentration reduction means such as carbon dioxide transmissible containers filled with carbon dioxide absorbing material
  • the amount of carbon dioxide absorbing material placed in the carbon dioxide transmissible containers should be sufficient to be capable of absorbing all the carbon dioxide that enters the carbon dioxide transmissible containers and therefore needs to be a sufficient amount to last the estimated time of storage of produce within the chamber.
  • the substance may be introduced independently of the oxygen removal.
  • a substance in which a substance is introduced into a chamber containing substantially non-respiring cargo, as described above it may be desired to have a modified atmosphere chamber in which carbon dioxide is present in the chamber at a concentration which does not substantially exceed a predetermined concentration.
  • carbon dioxide may be the introduced substance.
  • oxygen removal and carbon dioxide introduction may be effected by an artificial respiration load, that is an oxygen load which consumes oxygen and produces carbon dioxide. Possible artificial respiration loads have been discussed above.
  • the second aspect of the invention is applied to a chamber in which the introduced substance is carbon dioxide and where oxygen removal and carbon dioxide introduction are effected by an artificial respiration load
  • carbon dioxide will be a principal chamber atmosphere constituent and the method may further comprise removing carbon dioxide from the chamber atmosphere substantially at a predetermined carbon dioxide removal rate, the predetermined carbon dioxide removal rate having been selected such that the carbon dioxide concentration within the chamber atmosphere does not substantially exceed a predetermined amount lower than the carbon dioxide concentration which would result if no carbon dioxide removal was effected.
  • the predetermined carbon dioxide introduction rate and the predetermined carbon dioxide removal rate may be calculated in accordance with a mathematical model of the proportions of chamber atmosphere constituents.
  • the carbon dioxide removal rate is calculated from a formula that produces a result substantially equal to the result produced by a calculation in accordance with the following formula:
  • a co is the rate of carbon dioxide removal from the chamber atmosphere
  • R co is the carbon dioxide introduction rate
  • a 0 is the rate of oxygen gas removal from the chamber atmosphere
  • a ⁇ is the rate of removal from the chamber atmosphere of a further constituent of the input not being oxygen gas
  • X t 0 is the proportion of the further constituent in the input divided by the proportion of oxygen gas in the input;
  • p 0 is the oxygen setpoint expressed as a proportion
  • p co is the carbon dioxide concentration in the chamber atmosphere expressed as a proportion
  • ⁇ is the sum of the concentrations of any further principal chamber atmosphere constituents, expressed as proportions.
  • the oxygen level When the chamber of the present invention is to have an adjusted atmosphere where the oxygen concentration is maintained substantially at a predetermined concentration (the oxygen setpoint), in the absence of an inert gas purging operation, the oxygen level must first degrade from the atmospheric proportion (around 21%) to the setpoint.
  • the oxygen concentration control is based on having a substantially sealed chamber, then during the time the oxygen level degrades from the atmospheric proportion to the setpoint, the chamber will be substantially sealed.
  • release of the introduced substance at the rate determined in accordance with equation (1) may result in the concentration of the substance overshooting the desired equilibrium level of the substance.
  • the methods of the present invention may comprise the step of introducing the substance at a rate prior to the oxygen concentration attaining the setpoint which is different from the rate of introduction of the substance following the oxygen concentration attaining the setpoint.
  • I 0 is the initial normalised oxygen concentration in the chamber
  • p 0 is the oxygen setpoint
  • r 0 is the normalised rate of oxygen consumption through respiration (the normalisation being with respect to chamber volume) .
  • the variation of the concentration of the introduced substance is as follows:
  • R f exceed, —- . Consequently, if under these circumstances the release rate R f is set to k f k f ⁇ p , then overshoot will not occur ( p f here represents the level of the introduced substance that it is desired be maintained after the oxygen setpoint is reached, but not overshot beforehand) . Conveniently, the release rate R ⁇ - may simply be set to k f - p, eq prior to the oxygen setpoint being reached irrespective of whether overshoot would otherwise be expected to have occurred in order to ensure that overshoot will not occur.
  • a method for introducing a substance into the atmosphere within a chamber such that the concentration of the substance within the chamber atmosphere does not substantially exceed a predetermined amount, wherein the substance is introduced at one or more first release rates prior to the oxygen concentration attaining the oxygen setpoint and wherein the substance is introduced at one or more second release rates subsequent to the oxygen concentration attaining the oxygen setpoint.
  • the oxygen concentration control is based on one of the methods described above in which the chamber is not substantially sealed, then during the time the oxygen level degrades from the atmospheric proportion (or other initial proportion) to the setpoint, the chamber will be expected to have some leakage (since it is not substantially sealed) . However, the average flow rate out of the chamber will not be as high as when the oxygen setpoint is reached since the method of oxygen control will not be actively admitting ambient atmosphere and expelling chamber atmosphere until the setpoint is reached. Accordingly, during the time the oxygen concentration is degraded by the oxygen removal from its initial value to the setpoint, release of the introduced substance at the rate determined in accordance with equation (1) may result in the concentration of the substance overshooting the desired equilibrium level of the substance.
  • the rate of introduction of the substance will need to be reduced in comparison to that which is calculated for the case when the oxygen setpoint is reached (ie. the release rate determined in accordance with equation (1)).
  • the maximum concentration of the substance in the chamber is first determined for the case where there is some leakage from the chamber.
  • this circumstance is similar to that where a substance is introduced into a chamber that is not substantially sealed and that contains respiring produce, where no adjustment of the chamber atmosphere takes place. (In some circumstances it will be desirable to introduce a substance into a chamber that is not substantially sealed that contains respiring produce such that the concentration of the substance does not substantially exceed a predetermined amount, but without otherwise adjusting the chamber atmosphere.)
  • the concentration of the substance will be expected to reach (but will not substantially exceed) the following level: where f v is the normalised outflow rate of chamber atmosphere.
  • outflow may result from leakage from the chamber. Where atmosphere adjustment is not being effected, outflow may also result from leakage from the chamber. Where atmosphere adjustment is not being effected, outflow may result from forced ventilation. The nature of the outflow is not important.
  • the substance may be introduced at a rate such that the concentration of the substance does not substantially exceed a predetermined amount if the outflow rate of chamber atmosphere f v can be measured or pre-estimated (the other quantities in equation (12) being known or controllable) . Because the oxygen concentration in the chamber is relatively easy to measure, a convenient method for determining the chamber outflow rate may be based on the measurement of oxygen concentration and the knowledge, or an estimate, of the rate of removal of oxygen from the chamber, such as by respiration of produce or provision of an oxygen load.
  • the outflow rate is substantially constant for at least substantial periods of time. Where the outflow rate remains substantially constant within a given period, the outflow for that period may be used in calculations or estimates, and the outflow rates for other periods used for calculating or estimating outflow rates for such other periods.
  • the outflow rate f v can be calculated from the following expression, which depends only on the respiration rate and measured oxygen concentrations :
  • p 0 (t) is modeled as a straight line for the purposes of applying equation (13) so that its derivative p a ' (t) may be easily determined. Provided the time scale is sufficiently short, this approximation will not be unreasonable.
  • a method for introducing a substance into the atmosphere within a chamber such that the concentration of the substance within the chamber atmosphere does not substantially exceed a predetermined amount selection of the rate being calculated in dependence on a pre-estimate or a measurement of the outflow rate of chamber atmosphere from the chamber.
  • the outflow rate of chamber atmosphere from the chamber is calculated in dependence on measured concentrations of a different atmospheric constituent within the chamber atmosphere.
  • the different atmospheric constituent within the chamber atmosphere is oxygen.
  • the concentration of the introduced substance within the chamber atmosphere may be substantially zero at a particular time, such as by the end of the intended transit and/or storage time of items, such as produce, stored within the chamber.
  • concentration of the substance within the chamber atmosphere will decrease. Using a continuous flow model, the concentration of the substance will vary as follows after the substance introduction means is switched off or otherwise deactivated:
  • the initial concentration I is the concentration of the substance at the moment the substance introduction means is deactivated. If it is assumed that the substance concentration was approximately equal to the desired or estimated equilibrium concentration p , when the substance introduction means is deactivated (ie.
  • the substance concentration within the chamber will decrease from the initial concentration I ⁇ to the following levels after time has elapsed following deactivation of the substance introduction means:
  • the substance introduction means may be deactivated at a time of 3 ⁇ hours prior to the relevant time.
  • a controller includes sensor means and control means. Where oxygen concentration control is used, or when the controller must otherwise measure oxygen concentrations, the sensor means is operable for sensing the concentration of oxygen.
  • the sensor means may also sense other variables within the chamber, for example, humidity.
  • the sensor means includes an oxygen concentration measurement device which provides an output in the form of an electrical signal containing information about the oxygen concentration level within the chamber.
  • Such an electrical signal may be a direct current signal having voltage proportional to oxygen concentration or the signal may digitally encode the oxygen concentration level or a number that is proportional, or otherwise in known relation to, the oxygen concentration.
  • Other forms of output are also envisaged within the scope of the present invention.
  • a controller according to the present invention comprises means to receive and respond to the sensor means output. Such response may include activating devices subject to the control of the controller. The response may include activating one or more valves. It may include signalling the substance introduction means to commence introducing the substance, to halt introducing the substance, or to vary the substance introduction rate.
  • the controller may be operatively connected to the devices under its control by direct wire connection or any other suitable means.
  • the controller may receive signals from the sensor means continuously. It may sample the signals discontinuously. Where the signals are sampled discontinuously, the sampling intervals may be equal or unequal. The sampling interval may be made to vary according to the output of the sensor means or may be fixed.
  • the controller includes measurement memory for retrievably storing a series of measurements from the sensor means.
  • controller program is required to perform calculations in dependence on measured data (for example, a controller program implementing the method described with reference to equation (13)), the controller must include sufficient computing power to effect the calculations.
  • Suitable communication means may include telecommunications, mobile telephony, Internet connections, satellite transmissions, or any other suitable means for remotely communicating data, including any combination of the foregoing.
  • Sealing means is provided to seal the chamber to the required extent.
  • the chamber is preferably substantially sealed.
  • inlet means and/or outlet means are used in conjunction with an opening in the chamber and the chamber must be sealed to the extent that, when the pressure within the chamber is substantially equal to ambient pressure the rate of leakage of oxygen into the chamber is less than the rate of consumption of oxygen by the respiring produce, sealing means may be used or not, as necessary.
  • a chamber according to the present invention containing respiring produce is sealed to a sufficient extent that the rate of consumption of oxygen by the respiring produce within the chamber exceeds the rate of leakage of oxygen into the chamber.
  • the presently preferred testing method for use in relation to receptacles in the form of (empty) shipping containers is to first seal a container with sealing means according to the present invention (to be discussed below) . Following sealing, air is pumped into the container at a regulated flow rate through an appropriate fitting in an air vent in the container. At another air vent, there is provided a manometer tapping to measure the pressure inside the container.
  • the preferred testing method employs the principle that, at a constant pressure within the container, the flow rate into the container must equal the flow rate out of the container (through the various leakage paths) . Accordingly, the flow rate of air being pumped into the container is adjusted until the pressure remains constant at a particular target pressure, preferably 150 pascals above atmospheric pressure.
  • a container with a leakage rate of no more than about 10 to 12 litres per minute typically represents a container suitable for conversion to a substantially sealed chamber in accordance with the present invention, without any need for repair.
  • a container with a leakage rate of no more than about 20 to 25 litres per minute typically represents a container suitable for conversion to a substantially sealed chamber in accordance with the present invention without any need for repair. It will be appreciated by those skilled in the art that the appropriate degree of air tightness for a container depends upon whether the produce to be stored has a high or low respiration rate and that the figures quoted are only a guide.
  • the sealing means acts as a barrier to the passage of gas into or out of the chamber.
  • the sealing means may act as a moisture barrier.
  • the chamber may comprise substantially the entire internal volume of the receptacle or a reduced volume within the chamber.
  • the point of entry to a chamber is liable to leak.
  • the point of entry to a chamber is typically in the form of one or more doors.
  • the seals of the doors of the container are generally the source of most leakage. Consequently, the sealing means provided in accordance with the present invention may include door sealing means.
  • the sealing means provided by the present invention may also include a curtain.
  • the curtain may comprise a substantially fluid impervious sheet.
  • the curtain may substantially seal an open end of a receptacle to form the chamber.
  • the curtain may seal the chamber from leakage paths in the receptacle that are outside the chamber.
  • the curtain may seal the chamber from any leakage paths in the door seals of the receptacle by being interposed between the chamber and receptacle door.
  • a curtain may be attached to the internal and/or external walls of the receptacle by any suitable means.
  • Adhesive including tape or glue, may be used.
  • a curtain for use in conjunction with a receptacle made from a magnetic material, such as a steel shipping container.
  • the curtain is provided with numerous permanent magnets adjacent its periphery for attaching the curtain to the receptacle.
  • the curtain is installed in the container when the doors are open by attaching the magnets to the external walls of the container. Once the curtain is suitably placed, the doors of the container are closed to thereby substantially seal the curtain against the container.
  • a curtain according to one aspect of the present invention is preferably located close to the door of the receptacle in order to maximise the volume of the chamber.
  • the curtain is preferably approximately coplanar with the receptacle door when the curtain is in a substantially un-deformed state where there is equal pressure on either side of the curtain.
  • Refrigerated shipping containers are generally of a standard style of construction. Such containers typically have a false floor. The stored items, such as produce, sits on the false floor which is spaced from the outer wall of the container to facilitate air flow within the container. The false floor typically terminates a short distance from the end of the container to facilitate air flow at the ends of the load stored within the container.
  • the curtain is preferably located within the space between the container door and the beginning of the false floor.
  • the chamber is accordingly bounded by the container walls and the curtain with the space between the curtain and the container door being outside the chamber.
  • the sealing means provided in accordance with the present invention may also include a cover for any ventilation port in the shipping container or other receptacle.
  • the cover may comprise a sheet of flexible material such as an expanded rubber sheet.
  • the sheet may be initially oversized and subsequently trimmed on site to form a cover which matches the profile of the ventilation port whereby to seal it.
  • the cover may be installed over the ventilation port by any means.
  • the cover is adhered to the port and/or the wall immediately surrounding the port with tape and/or glue.
  • a port comprises a number of apertures, one or more covers may be used to seal the port.
  • the cover is substantially impermeable.
  • the cover may include one or more layers which are not substantially impermeable.
  • the cover may include a substantially impermeable layer such as an adhesive sheet to adhere the cover to the port and/or the wall immediately surrounding the port.
  • the substantially impermeable adhesive sheet is preferably applied so as to substantially cover the permeable material. In this way the cover may be rendered substantially impermeable.
  • Openable and closeable inlet and outlet means provided in accordance with the present invention are operable to facilitate respectively the inflow of ambient atmosphere into the chamber and the outflow of chamber atmosphere from the chamber.
  • Inlet and outlet means each comprise one or more valves operable to provide in an open position communication between the chamber atmosphere within the chamber and the ambient atmosphere surrounding the chamber.
  • Inlet means and outlet means may be located in any boundary of the chamber.
  • the outlet means is located adjacent to a fan provided in the chamber for circulating air within the chamber.
  • the outlet means is mounted in a ventilation port near the fan.
  • the outlet means is preferably mounted in the ventilation port that is typically located adjacent to the fan.
  • the outlet means is preferably located on the high pressure side of the fan so that when the outlet is open, chamber atmosphere is forced out of the chamber.
  • the inlet means is preferably spaced from the outlet means.
  • the arrangement of the inlet means and outlet means is such as to facilitate the free flow of atmosphere between the interior and exterior of the chamber.
  • the inlet and outlet means are positioned relative to one another so as to facilitate cross-flow ventilation when each is in the open position.
  • the inlet and outlet means are located at either end of the chamber.
  • the inlet means or outlet means may be mounted in a curtain according to the present invention.
  • installation of the curtain also includes installation of the inlet means or outlet means.
  • the inlet means and the outlet means may each include a plurality of valves. Such valves may be spaced from one another in locations which facilitate the desired air flow.
  • valves comprising the inlet and outlet means may be operable in response to a signal from the controller.
  • Each valve may communicate with the controller by wire or any other suitable means.
  • Each valve provided according to the present invention may be magnetically operable between an open position and a closed position.
  • a solenoid is preferably provided to generate a magnetic field in response to the application of a direct current whereby to urge the valve toward an open or a closed position dependent upon current direction.
  • Valves suitable for comprising inlet and outlet means according to the present invention are preferably electromagnetically actuable valves having a solenoid so that they may be opened from a closed position and closed from an open position by applying direct electric current to the solenoid, said one or more valves being held in either the open position or the closed position in the absence of the application of said direct electric current.
  • Valves according to the present invention preferably may be both opened from a closed position and closed from an open position by applying a pulse of direct electric current to the solenoid.
  • the valves are adapted to be held in the closed position or the open position in the absence of an electric current in the solenoid by magnetic forces.
  • the member is a slidable within the bore.
  • the slidable member carries at least one cover adapted to cover each said at least one aperture to prevent fluid passing through said at least one aperture.
  • a valve comprising the inlet or outlet means comprises at least one aperture through which fluid may pass to pass through the valve, a solenoid to generate a magnetic field in response to the application of a direct electric current and a flap which is adapted to move in response to said magnetic field between a valve open position wherein fluid may pass through the valve through said at least one aperture and a valve closed position wherein the flap prevents fluid passing through the valve through any said at least one aperture.
  • the solenoid is located between the flap and a member carried by the flap, the member and the flap each having a permanent magnet so arranged that when a direct electric current is passed through the valve in one direction the solenoid attracts the magnet on the member and repulses the magnet on the flap in order to move the flap to a valve open position and when a direct electric current is passed through the solenoid in a direction opposite to said one direction the solenoid repulses the magnet on the member and attracts the magnet on the flap in order to move the flap to a valve closed position.
  • a valve comprises a magnetic member moveable along a bore in response to the field generated by passing a direct current through a solenoid surrounding the bore. The member may be captured within the bore and moveable between positions which open and close the valve.
  • the magnetic member may take any suitable shape.
  • the magnetic member may be a ball. It may be a right circular cylinder. It may be a prismatic member having a cross-section of any suitable shape. Other magnetic member shapes are envisaged within the scope of the invention.
  • the magnetic member is in the form of a ball.
  • the valve contains a hole through which fluid must pass to pass through the valve.
  • the ball seals the valve by sealingly abutting the edge of the hole.
  • the hole is a hole in a plate in the valve.
  • the diameter of the ball is greater than the diameter of the hole.
  • the magnetic member is in the form of a member which is slidable with respect to the valve body.
  • the slidable member is a cylindrical rod.
  • the slidable member carries a cover with a sealing surface.
  • the cover is a panel with an annular sealing surface.
  • the fluid path through the valve when the valve is open includes one or more holes.
  • the holes are holes in a plate in the valve.
  • the cover seals the valve by sealingly abutting the surface around the holes.
  • the valve is closed by the annular sealing surface sealingly abutting the surface around the holes.
  • the outer diameter of the annular sealing surface is greater than the diameter of a circle surrounding the hole or holes.
  • the inner diameter of the annular sealing surface is also greater than the diameter of a circle surrounding the hole or holes.
  • the valve comprises a flap moveable under the application of a magnetic field between open and closed positions.
  • the flap may carry a magnet.
  • the flap may be hingedly mounted with respect to a base.
  • the base may carry a solenoid or coil for generating a magnetic field to open or close the flap and hence the valve in response to a signal from the controller.
  • a valve according to the present invention may be provided with a casing. Any such casing must allow sufficient fluid flow through the valve when the valve is open.
  • the casing may only partially encase the valve.
  • the casing may be apertured.
  • a casing may contain holes. Such holes may be any suitable shape. They may be circular. They may be slots. Other aperture shapes are envisaged within the scope of the invention.
  • a valve according to the present invention has an apertured casing
  • the apertures are located so that any relative movement between the valve and the contents of the chamber or another part of the chamber will not prevent fluid flowing through the valve when the valve is open.
  • the apertures are located so that the apertures will not be obstructed so as to ensure that the flow of fluid is not restricted to any significant extent.
  • the casing includes apertures on the side of the valve rather than, or in addition to, the front or back face of the valve so that if the valve moves so that the front or back face abuts the door or another object with its front or back face, the apertures will not thereby be obstructed.
  • the differential between the pressures of the atmospheres on each side of the curtain may vary at different points on the curtain. This variation can cause the curtain to move somewhat erratically.
  • the curtain may be provided with inlet means or outlet means in the form of valves, or openings, that are spaced apart.
  • a curtain may carry inlet means or outlet means in the form of a pair of valves. One valve may be located in the upper portion and the other in the lower portion of the curtain.
  • outlet means may be located in a curtain according to the present invention and the inlet means may be located near the fan.
  • the inlet means communicates with one of the apertures of the ventilation port that is located near the fan provided in the chamber for circulating air within the chamber.
  • Such an inlet means is to be located on the low pressure side of the fan so that when the inlet means is open, the atmosphere outside the chamber is pushed into the chamber.
  • outlet means may be mounted in a curtain according to the present invention.
  • figure 1 is a schematic side view of a standard refrigerated container fitted with atmosphere adjustment apparatus according to an embodiment of the present invention.
  • Figure 1 shows a receptacle in the form of refrigerated container 10 which includes refrigeration unit 12, doors 14 and ventilation port 18.
  • Container 10 has been converted into an adjusted atmosphere chamber 11.
  • the atmosphere adjustment apparatus installed in container 10 are to adjust the chamber atmosphere so that is has a desired oxygen concentration and a desired carbon dioxide concentration and so that a fungicide may be applied to the chamber in such a manner that its concentration will not substantially exceed a predetermined level, subject to the additional constraint that the fungicide concentration in chamber 11 is to be substantially zero when container 10 reaches its destination.
  • Sealing means is provided in the form of a curtain 16 and a cover (not shown) for ventilation port 18.
  • Curtain 16 is an impervious sheet, and is attached to the external walls of container 10 with numerous permanent magnets mounted on the curtain adjacent its periphery. Curtain 16 is installed in the container when the doors are open by attaching the magnets to the external walls of the container. Once the curtain is suitably placed, the doors are closed to thereby substantially seal the curtain against the container. Installation of the curtain in the container defines a chamber 11 within the container.
  • the cover for ventilation port 18 located at the machinery end of container 10 comprises an impervious plastic sheet adhered with tape to the wall of container 10.
  • the cover is adapted to cover, and hence seal, ventilation port 18.
  • the cover is fitted with outlet means in the form of a valve 20.
  • Valve 20 is located on the high pressure side of the fan so that when valve 20 is open, the chamber atmosphere is forced out of the chamber.
  • Controller 8 includes sensor means (not shown) in the form of an oxygen concentration measurement device.
  • the sensor means takes oxygen concentration measurements at equally spaced intervals (which may be adjusted) .
  • the cargo is to comprise respiring produce.
  • the desired oxygen setpoint, desired equilibrium carbon dioxide concentration and desired fungicide concentration are determined based on the particular type of produce forming the cargo.
  • Carbon dioxide reduction means 9 comprising a quantity of hydrated lime held in carbon dioxide transmissible bags is located within chamber 11.
  • the quantity of lime, the size and number of lime bags and the carbon dioxide transmissibility of the bags are determined as described above (ie. as described with reference to equation (8)) based on the desired oxygen setpoint, desired equilibrium carbon dioxide concentration, desired fungicide concentration and predicted produce respiration rate.
  • Oxygen concentration control is effected as follows. If the oxygen concentration falls below a predetermined value (for example, 5%) then controller 8 sends a signal via wires 17 to open valves 100 and 20. This allows the inflow of ambient atmosphere into chamber 11 through valves 100 and the outflow of chamber atmosphere from chamber 11 through valve 20.
  • a predetermined value for example, 5%
  • Valves 20 and 100 are controlled by the controller according to the following logic:
  • controller 8 opens valves 20 and 100 to allow ambient air to enter the chamber to thereby increase the oxygen concentration within the chamber. (For the avoidance of doubt, the reference to "0.9%" is in units of chamber oxygen concentration and does not represent a proportion of the oxygen setpoint.) Valves 20 and 100 are closed after controller 9 senses that the oxygen concentration has exceeded the oxygen setpoint.
  • controller 8 opens valves 20 and 100 to allow ambient air to enter the chamber to thereby increase the oxygen concentration within the chamber. Controller 8 closes valves 20 and 100 after a time that is dependent on the oxygen concentration as measured by the controller 8 prior to opening the valves, as follows:
  • Valves 20 and 100 are both electromagnetically actuable valves and thus each include a solenoid. These valves are arranged so that the application of direct electric current in one direction opens the valves and the application of direct electric current in the opposite direction closes the valves. The valves are arranged to be held by permanent magnets in either the open position or the closed position in the absence of the application of the direct electric current, in order to reduce the power requirements of the controller.
  • the oxygen concentration within the chamber will be the same as the concentration of oxygen in ambient air (ie. approximately 21%).
  • the valves 20 and 100 will accordingly remain shut at least until the oxygen concentration within the chamber reaches the setpoint.
  • Fungicide is introduced into the atmosphere of chamber 11 by means of atomiser 30.
  • Atomiser 30 is connected to controller 8 by wires 31-
  • the controller is programmed to cause atomiser 30 to release fungicide at a first predetermined constant release rate R ⁇ of k, • p , eq (as described above with reference to equation (11)) prior to controller 8 sensing that the oxygen setpoint has been reached.
  • Controller 8 is programmed to change the fungicide release rate R. to a second predetermined constant release rate once controller 8 senses that the oxygen setpoint has been reached, the rate being determined in accordance with equation (2) above.
  • Controller 8 is programmed to switch off atomiser 30 at a time of 3x prior to the expected destination time, where ⁇ is determined in accordance with equation (16), so that the fungicide concentration will be substantially zero at the required time.
  • R f (t ') dt ' is the normalised accumulation within the chamber of fungicide
  • I O f (t ') dt ' is the normalised quantity of fungicide adsorbed on the surfaces
  • Equation (1.5) thus tends towards an equilibrium level of:
  • r 0 is the normalised respiration rate of produce in the chamber.
  • equation (2.1) If f (0 and / (0 are both zero (ie. the chamber is sealed), then equation (2.1) becomes:
  • Equations (1.6), (2.3), (3 2) and (4.3) give rise to a simple model for the case when all atmospheric constituents are at equilibrium. Manipulation of these expressions yields the following expressions, respectively, for fungicide release rate and carbon dioxide absorption rate:
  • one method of avoiding overshoot is to set the fungicide release rate during the period when the chamber is sealed to the following:
  • the fungicide release rate can be changed to the value given by equation (5.1).
  • the fungicide concentration in the chamber may be estimated based on an estimate of the outflow rate from the chamber f .
  • / may be estimated from knowledge of r Q and measurement of p 0 (and calculation of p 0 ' from p Q ).
  • p 0 (t) is modelled as a straight line (which will be a reasonable approximation over sufficiently short time scales) then / may be easily estimated from the measurement of oxygen concentrations.
  • the appropriate fungicide release rate can be calculated based on the desired fungicide concentration, as follows:

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  • Polymers & Plastics (AREA)
  • Cold Air Circulating Systems And Constructional Details In Refrigerators (AREA)

Abstract

Appareil et procédé pour introduire une ou plusieurs substances aéroportées telles qu'un insecticide, fongicide, fumigant ou bactéricide dans une atmosphère d'oxygène contrôlée (11) à l'intérieur d'une chambre (10) et ajuster l'atmosphère dans la chambre de manière à ce que la concentration de la substance ne dépasse pas sensiblement une quantité prédéterminée. La substance peut être du dioxyde de carbone. Elle peut se présenter comme un liquide et être introduite sous forme de brume, de brouillard pulvérisé ou par vaporisation. Le procédé consiste en ce qui suit: (a) veiller à ce que la concentration d'oxygène corresponde à une valeur prédéterminée en surveillant la concentration d'oxygène et, après la détection d'une baisse de la concentration d'oxygène en dessous d'une valeur prédéterminée, admettre une entrée contenant de l'oxygène et permettre à l'atmosphère de la chambre de s'échapper; (b) évacuer l'oxygène de l'atmosphère de la chambre avec un débit suffisant pour assurer l'admission continue de l'entrée dans la chambre, de manière à ce que la concentration d'oxygène corresponde à la valeur prédéterminée; et (c) introduire la substance dans l'atmosphère de la chambre avec un débit prédéterminé.
PCT/AU2001/001431 2000-11-08 2001-11-07 Insecticide / fongicide introduit dans une chambre a atmosphere controlee Ceased WO2002038467A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002213671A AU2002213671A1 (en) 2000-11-08 2001-11-07 Insecticide/fungicide introduced into controlled atmosphere chamber

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPR1358 2000-11-08
AUPR1358A AUPR135800A0 (en) 2000-11-08 2000-11-08 Dosing system

Publications (1)

Publication Number Publication Date
WO2002038467A1 true WO2002038467A1 (fr) 2002-05-16

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU2001/001431 Ceased WO2002038467A1 (fr) 2000-11-08 2001-11-07 Insecticide / fongicide introduit dans une chambre a atmosphere controlee

Country Status (2)

Country Link
AU (2) AUPR135800A0 (fr)
WO (1) WO2002038467A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005053955A1 (fr) * 2003-12-03 2005-06-16 Commonwealth Scientific And Industrial Research Organisation Procedes de production de materiau d'emballage servant au transport et au stockage de marchandises perissables
CN103977925A (zh) * 2014-05-23 2014-08-13 国家海洋局天津海水淡化与综合利用研究所 一种喷淋密度测控装置及其测控方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU6006290A (en) * 1989-08-08 1991-02-14 Linde Aktiengesellschaft Method of pest control in granular foodstuffs during their storage in containers
WO1991011913A1 (fr) * 1990-02-13 1991-08-22 The Broken Hill Proprietary Company Limited Production d'une atmosphere regulee utilisee pour l'entreposage de produits d'horticulture
EP0136042B1 (fr) * 1983-09-01 1992-01-08 Transfresh Corporation Procédé de transport de comestibles et conteneur adapté pour la réalisation de ce procédé
US5799495A (en) * 1996-10-30 1998-09-01 Nitec, Inc. Container oxygen control system for transporting and ripening perishable goods
WO2000023350A1 (fr) * 1998-10-19 2000-04-27 Mitsubishi Australia Ltd Dispositif de mise a l'air libre commandee d'une chambre

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0136042B1 (fr) * 1983-09-01 1992-01-08 Transfresh Corporation Procédé de transport de comestibles et conteneur adapté pour la réalisation de ce procédé
AU6006290A (en) * 1989-08-08 1991-02-14 Linde Aktiengesellschaft Method of pest control in granular foodstuffs during their storage in containers
WO1991011913A1 (fr) * 1990-02-13 1991-08-22 The Broken Hill Proprietary Company Limited Production d'une atmosphere regulee utilisee pour l'entreposage de produits d'horticulture
US5799495A (en) * 1996-10-30 1998-09-01 Nitec, Inc. Container oxygen control system for transporting and ripening perishable goods
WO2000023350A1 (fr) * 1998-10-19 2000-04-27 Mitsubishi Australia Ltd Dispositif de mise a l'air libre commandee d'une chambre

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005053955A1 (fr) * 2003-12-03 2005-06-16 Commonwealth Scientific And Industrial Research Organisation Procedes de production de materiau d'emballage servant au transport et au stockage de marchandises perissables
CN103977925A (zh) * 2014-05-23 2014-08-13 国家海洋局天津海水淡化与综合利用研究所 一种喷淋密度测控装置及其测控方法

Also Published As

Publication number Publication date
AUPR135800A0 (en) 2000-11-30
AU2002213671A1 (en) 2002-05-21

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