Measuring and testing – Gas analysis
Reexamination Certificate
2000-03-10
2001-06-05
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
C422S078000, C436S135000
Reexamination Certificate
active
06240767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates generally to system for monitoring and controlling low concentrations of reactive gasses and, more particularly, to a system for monitoring and controlling concentrations of ethylene gas.
2. Related Art
Perishable produce such as fruit, vegetables and cut flowers, must be consumed while fresh. To facilitate this, an elaborate distribution system has been developed to deploy rapidly harvested produce into supermarkets, restaurants, and other food stores. Produce that is not timely consumed must be destroyed or otherwise discarded. Optimal flow of produce through this distribution chain is important to minimize the amount of produce that must be discarded.
It is well known that the rate at which the produce ages may be controlled by controlling the concentration of ethylene in the atmosphere surrounding the produce. This is related to the fact that ethylene is a plant growth hormone. For many products, exposure to ethylene, even in low concentrations, speeds the aging process. If ethylene concentration levels are not controlled and rise above unacceptable levels, premature ripening or decay of the produce can occur, which may require the produce to be discarded before it is able to be sold.
It has been found that reducing the concentration of ethylene is important during transportation and storage of produce that naturally emits ethylene gas. For example, ventillating to remove excess ethylene has been found to reduce the rate of decay for many fruits and vegetables and is also particularly useful for maintaining the robustness of cut flowers, such as tulips, imported into the United States from Holland.
It is sometimes financially advantageous to pick oranges while still green and cause the peel to change color subsequent to harvesting. As is well known, exposing a green colored orange to a low concentration of ethylene gas over a long period of time (24-72 hours) causes the chlorophyll in the orange peel to break down, thus causing the orange peel to change color. This process will be referred to herein as “degreening.”
Ethylene concentration between about 5 to 10 parts per million (ppm) affect the chlorophyll in the peel without penetrating into the fruit itself. Higher concentrations of ethylene, above about 10-15 ppm, however, have been found to cause the peel to break down and may cause the onset of mold in the peel. When this happens, the entire batch of fruit frequently must be discarded. By contrast, an insufficient amount of ethylene, below about 5 ppm, will delay the degreening process, thus inhibiting distribution of the current batch of fruit as well as batches of fruit waiting to enter the degreening rooms. Accordingly, controlling the concentration of ethylene during the degreening process is critical.
Controlling the concentration of ethylene has yet another use. Since ethylene is a plant growth hormone, increasing the concentration of ethylene may speed the ripening process for certain types of products. For example, it has been found that exposing tomatoes and bananas to ethylene in a concentration of about 100 ppm for a period of 12-24 hours will speed the ripening process for these products. Typically, a stepped process is used whereby the concentration is varied over time. Likewise, it is thus envisioned that controlled levels of ethylene gas could be used to stimulate plant production in outer space, should this ever become a reality.
Thus, monitoring and controlling the concentration of ethylene is important in many situations, especially during the production, transportation and storage of produce, during degreening of oranges, while ripening tomatoes and bananas and, potentially, in connection with growing plants in a controlled environment such as outer space. Unfortunately, detecting accurately ethylene concentrations, especially at the very low levels associated with degreening, is not trivial. Accordingly, there is a need for a system that can accurately monitor and control low concentrations of ethylene gas.
SUMMARY OF THE INVENTION
The present invention is a system that can accurately monitor and control low concentrations of ethylene gas. In one embodiment, a method includes reacting ozone and ethylene gas, detecting light produced by the reaction, and processing the detected light to determine a concentration of the ethylene gas. The method may also include controlling the concentration of the ethylene gas.
In another embodiment, an apparatus includes a test chamber configured to receive sample gas potentially containing an ethylene concentration and ozone, a light detector configured to receive light produced during a reaction between the ethylene and ozone and to produce signals related thereto, and a processor connected to the detector to process the signals to determine therefrom a value of the concentration of ethylene in the sample gas. The processor may be a general purpose computer running software configured to process the signals or a programmable logic controller.
In another embodiment, a supply for a testing device includes a four way valve configured to receive pressurized gas at one input and a test chamber having a piston journaled therein. A drive end of the piston is disposed in a drive chamber and a reaction end of the piston defines, with walls of the test chamber, a variable volume reaction chamber. The drive end of the piston is pneumatically connected to two ports of the four way valve to provide motive force to the piston. A manifold is connected to the variable volume reaction chamber, and is configured to receive sample gasses from at least one of a plurality of ports.
The supply may optionally contain a number of additional features, such as a vacuum pump connected to a port of the manifold, an ozone generator coupled to the variable volume reaction chamber to supply ozone to the variable volume reaction chamber, and a light detector such as a photo multiplier tube attached to the variable volume reaction chamber to receive light produced by a reaction between the sample gas and the ozone gas in the variable volume reaction chamber.
A computer may be configured to receive data indicative of light produced by the reaction from the light detector and to output information indicative of the concentration of ethylene gas in the sample gas. The computer may optionally be configured to receive data indicative of light produced by the reaction from the photo multiplier tube and to control the concentration of ethylene gas in an environment from which the sample gas was drawn. Control may be accomplished by injecting additional ethylene gas, e.g., by opening a supply valve, by maintaining the level of ethylene by regulating the flow of ethylene into the room or by decreasing the level of ethylene in the room by a combination of regulating the flow of ethylene into the room and ventilating the room.
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* Finlayson et al., “Low-Pressure Gas-Phase Ozone-Olefin Reactions. Chemiluminescence, Kinetics and Mechanisms”, Journal of the American Chemical Society/96:17/, Aug. 21, 1974, pp. 5356-5367.
* Toby, “Chemiluminescence in the Reactions of Ozone”, Chem. Rev. 84, 1984, pp. 227-285.
International Search Report dated Feb. 24, 2000.
Kane James A.
Nelson Bruce N.
Richard, II Roy V.
Morris James H.
Politzer Jay I.
Williams Hezron
Wolf Greenfield & Sacks P.C.
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