JPH04346774A - Storage apparatus for regulating atmosphere - Google Patents

Abstract

PURPOSE:To obtain the subject compact apparatus capable of being readily installed in a refrigerator by providing a container of a hermetically sealed structure having a lid with two separation membrane modules, a pump and an oxygen sensor for feeding a control signal to the pump according to a zirconia solid electrolytic method. CONSTITUTION:A storing container 1, having a hermetically sealed structure with a lid and equipped with two separation membrane modules 2 and 3, a pump 5 connected thereto and an oxygen sensor 6 for sending a control signal to the pump 5 according to a zirconia solid electrolytic method is housed in one corner of a room at a temperature within the region of 3 to 10 deg.C in a refrigerator constructed from partitioned plural rooms. The interior of the storing container 1 is enriched with nitrogen by setting a nitrogen concentrating module 2 on the outside of the container 1 and a module 3 for removing oxygen on the inside of the container 1, then connecting both with a tube 4, sucking the interior with the pump 5, further sensing the oxygen concentration in the interior of the container 1 with the oxygen sensor 6 and controlling the pump 5 with its electric signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmosphere-controlled storage device.

0002

BACKGROUND OF THE INVENTION In general, fruits and vegetables and processed foods are stored at low temperatures to prevent loss of freshness and spoilage. However, even in this case, if oxygen is present in the atmosphere, processed foods and the like will undergo oxidative deterioration due to the respiration effect of fruits and vegetables. To prevent this, it is necessary to appropriately lower the oxygen concentration in the atmosphere. It is advantageous to use nitrogen enrichment technology as a means for this purpose, and we decided to apply it to household refrigerators. In addition, the controlled atmosphere storage method is an energy-saving storage method, and is expected to become popular among producers and the distribution field in the future.

[0003] Conventionally known examples of CA storage for home use include Japanese Patent Application Laid-Open No. 14749/1982 and Japanese Utility Model Application No. 136378/1999, but these both use pressure-sensitive carbon storage using molecular sieve activated carbon for nitrogen enrichment. Differential adsorption method (hereinafter abbreviated as PSA method)
The gas with a nitrogen concentration of 90% or more obtained by this device is used to adjust the entire refrigerator or separated spaces to a low-oxygen atmosphere, and the food stored is limited to fruits and vegetables such as vegetables and fruits. Ta.

0004

[Problem to be solved by the invention] Since the nitrogen enrichment device using the PSA method consists of two adsorption towers and a compressor, the device itself is quite large, and it is installed in the box structure of the current refrigerator. It is quite difficult to do so, and if you try to incorporate it, that part will protrude, so it is desirable to downsize the device.

[0005] In addition, atmospheric storage has the effect of extending the shelf life of processed foods other than fruits and vegetables and seafood by appropriately adjusting the oxygen concentration. It is necessary to maintain the concentration within a certain range. In this case, the storage container is not necessarily one that is fixed to the refrigerator, but also a removable storage container or a bag that is highly flexible may be convenient for ease of use.

[0006]

[Means for solving the problem] When obtaining nitrogen-enriched gas using the PSA method, it is necessary to ensure the capacity of the adsorption tower in order to maintain performance, and there is a limit to the size of the compressor, and the overall equipment It is quite difficult to miniaturize. As an alternative to this, a nitrogen enrichment method using a separation membrane may be considered. That is, nitrogen enrichment progresses by setting two membrane modules assembled on a flat plate inside and outside a storage container, and sucking air with a pump attached to the end of the connected system. A zirconia solid electrolytic oxygen sensor is used to detect the oxygen concentration in the atmosphere at this time.

[0007] For some foods, the oxygen concentration must be lowered even further. In that case, the separation membrane method is not practical, so a PSA nitrogen enrichment device is installed separately from the refrigerator itself, and a plastic container or bag equipped with a fitting that allows one-touch connection of the nitrogen-enriched air obtained from the PSA nitrogen enrichment device is placed in the refrigerator. Make sure to store it in In this case as well, the internal oxygen concentration is detected by a zirconia solid electrolyte type oxygen sensor at the exhaust port through which atmospheric air is discharged, and the pump is controlled to adjust to the target oxygen concentration.

[0008]

[Operation] The separation membrane used to separate oxygen and nitrogen in the air is an organic thin film such as cellulose acetate or silicone (0.
1 to 0.3μ), and can be combined with a storage container to create a compact system.

The principle of membrane separation is to utilize the difference in the rate at which oxygen and nitrogen permeate through a thin membrane, and the permeation rate and separation coefficient (PO2/PN2) determine performance. To enrich the atmosphere inside the storage container with nitrogen, it is sufficient to set a module for nitrogen concentration outside the container and a module for oxygen removal inside the container, connect the two with a tube, and introduce them to a pump for suction. The oxygen concentration in the container is detected by an oxygen sensor, and the pump is controlled by the electrical signal. The oxygen sensor uses a zirconia solid electrolyte as a sensor element, and when voltage is applied to this element, an ionic current with oxygen ions as carriers flows, and the output current at this time shows a limiting current depending on the oxygen concentration. The current value is detected and fed back to the pump to control operation and maintain the oxygen concentration in the atmosphere within a certain range.

[0010] If it is desired to further increase the nitrogen concentration in the atmosphere, a PSA device is used. In this case, since it is separate from the refrigerator, food is placed in containers or bags that can be easily attached to and removed from the refrigerator, and then the air inside is replaced with nitrogen-enriched air generated by the PSA device and placed in a designated place inside the refrigerator. Make sure that it can be paid within. At this time, the container or bag should be equipped with a joint that can be installed and removed with one-touch operation in order to take in the nitrogen-enriched air of the PSA device, and that the valve can be opened and closed automatically.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

<Embodiment 1> An embodiment of the atmosphere storage method according to the present invention will be explained with reference to FIGS. 1 to 4. Figure 1 is a diagram of the basic structure of the atmosphere adjustment system, Figure 2 is a diagram of the structure of a nitrogen and oxygen separation membrane module, Figure 3 is a diagram of the structure of a zirconia solid electrolyte oxygen sensor, and Figure 4 is a diagram of a refrigerator equipped with this atmosphere adjustment system. FIG.

The atmosphere adjustment system is composed of a storage container 1, an external separation membrane module 2, an internal separation membrane module 3, a connecting tube 4, a pump 5, and an oxygen sensor 6. When the pump 5 is activated here, air flows along the membrane surface of the external separation membrane module 2. As shown in FIG. 2, the structure of the separation membranes 2 and 3 consists of three layers: a silicone polymer membrane 2a, a polysulfone porous membrane 2b, and a polypropylene nonwoven fabric 2c. Here, the silicone membrane has high gas permeability,
Since there is a difference in the affinity between oxygen and nitrogen, most of the oxygen permeates through the membrane and flows to the pump side, and the nitrogen-enriched air enters the storage container 1 and further oxygen permeates through the internal separation membrane module 3. Since it is removed, the nitrogen concentration will increase. The oxygen concentration within the container at this time is detected by an oxygen sensor 6 using a zirconia solid electrolysis method. Oxygen sensor 6 includes stabilized zirconia 7, cathode 8, anode 9, and DC power source 1.
0, a heater 11, a ceramic case 12, and a camp 13. If the atmosphere contains oxygen, the oxygen ions receive electrons at the cathode 8 and become oxygen ions, which move through the solid electrolyte of stabilized zirconia 7 and release electrons at the anode 9, returning to oxygen. At this time, an electromotive force is generated according to the difference in oxygen partial pressure between the cathode side and the anode side, so this is extracted as an output and the oxygen concentration is within a certain range (02:6~10
%), start and stop the pump 5. Note that the output of the zirconia oxygen sensor decreases at low temperatures, so it is heated with a heater 11 (3W) and used at about 300°C. When this heat dissipates, the temperature inside the container will rise, so a ceramic case 12 is used to shield it.
cover with

The storage container 1 systemized in this way is installed in the refrigerating compartment 15 of the refrigerator 14. This storage container 1
There is a door 16 on the front that can be moved forward, and the door has a stopper 17.
A packing 18 is interposed between the container and the door to maintain airtightness. In order to facilitate the loading and unloading of food, a storage box 19 is further provided inside the container and is pulled out to the front. Note that although the storage container 1 was installed in the refrigerator compartment 15 this time, the installation location is not limited to this, and the characteristics of this storage method can be utilized as long as it is used in a temperature range of 5 to 10°C.

<Embodiment 2> An embodiment of the present invention is shown in FIGS. 5 to 7. In this embodiment, the atmosphere inside the storage container 20 and the bag 30, which can be easily attached to and detached from the refrigerator, is adjusted using a PSA type nitrogen enrichment device 20 that is independent from the refrigerator main body. Furthermore, it is possible to lower the oxygen concentration, and moreover, it is intended to improve usability.

The PSA nitrogen enrichment device 20 includes an adsorption tower 21
, an adsorption tower 21 is filled with molecular sieving carbon, and when compressed air is fed, only oxygen is adsorbed and retained, nitrogen-enriched air is generated, and is taken out through a tube 24 connected to an outlet 23. Can be done.

The storage container 25 is made of plastic and is provided with an air inlet 26 and an outlet 28 opposite thereto, and the lid of the container is fixed with a stopper 29 to maintain airtightness. The tube from the nitrogen enrichment device and the storage container inlet 26 can be connected with a single touch using a joint 27. An oxygen sensor 6 is also attached to the discharge port 28 via a one-touch joint 27, and if the oxygen concentration is set to a desired value in advance, the PSA device 20 will automatically stop, and the tube 24,
Remove the oxygen sensor 6 and place it inside the refrigerator.

The storage bag 30 is made of vinyl such as vinylidene chloride and is provided with an air inlet 31 and an air outlet 32, and is kept airtight by closing a zipper 33. Even in this case, the tube 24 and the oxygen sensor 6 can be connected with one-touch fittings. The joint has a structure as shown in Figure 8, with a push rod 27a and a valve 27b.
, a spring 27c, an O-ring 27d, etc., and when the enrichment device side is inserted into the storage container side, the valve 27 is closed with a push rod 27a.
Air flows through the gap created by pressing b. When removed, the valve 27b is closed and sealed by the action of the spring.

Example 3 In the atmosphere adjustment system shown in FIG. 1, the pump 5 (flow rate 12 l/min, ultimate vacuum -7
10 mmHg) to adjust the oxygen concentration in the storage container. FIG. 9 shows the relationship between operating time and oxygen concentration when the internal volume of the container was changed from 10 to 50 liters. From this, it can be seen that if the internal volume is about 30 liters, the oxygen concentration will be about 10% after 1.5 hours of operation.

[0020] Put spinach and honey leaves in a container and add 1 oxygen
It was adjusted to 0% and stored at a temperature of 5°C for 4 days. In addition, a sashimi platter (tuna, yellowtail, shrimp, squid, octopus, toppings) was similarly adjusted to 10% and stored at -1°C for 8 days. When we observed the appearance of vegetables stored under the same conditions in an atmospheric atmosphere, we found that compared to spinach and mitsuha, the yellowing and wilting of the comparison vegetables were suppressed, and in the case of sashimi, tuna, yellowtail, and
There was little discoloration of shrimp, ingredients, etc.

<Example 4> PSA type nitrogen enrichment device 20
The atmosphere of the storage container 25 is changed to a nitrogen concentration of 9 using the air generated in
Bonito flakes, ham, sockeye salmon, open horse mackerel, etc. were stored at -1°C for 7 days at a concentration of 9% or higher. When compared with those stored in the same manner in the air, all of them maintained their original appearance and showed little discoloration or fading. Furthermore, when steamed bread and rice cakes were stored for 10 days at room temperature in a nitrogen atmosphere with a nitrogen content of 90% or higher, the ones stored in the air developed mold, but the ones in which the atmosphere was adjusted did not develop mold at all.

[0022]

Effects of the Invention According to the present invention, since it is a compact atmosphere adjustment system that incorporates a nitrogen-oxygen separation membrane in a storage container, it can be easily installed in a refrigerator, and the synergistic effect of temperature and atmosphere improves the flavor of food. It is now possible to store for a long time without losing freshness.

[0023] Furthermore, by using a PSA nitrogen enrichment device separate from the refrigerator, the nitrogen concentration in plastic containers and bags can be adjusted to any value up to 99%, so fruits and vegetables, seafood, meat, and processed foods can be It is possible to use it flexibly and economically by storing it in the refrigerator or at room temperature depending on the season and the nitrogen concentration depending on each food. Furthermore, since a zirconia solid electrolyte, which has excellent linearity and responsiveness and is easy to maintain, is used to adjust the nitrogen concentration, the effect of the atmosphere-controlled storage method is further ensured, and it is advantageous in terms of energy saving.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of an atmosphere system according to an embodiment of the present invention;

[Figure 2] Explanatory diagram of nitrogen-oxygen separation membrane module,

[Figure 3
]Explanatory diagram of a zirconia solid electrolyte oxygen sensor,

FIG. 4 is a cross-sectional view of a refrigerator equipped with the atmosphere adjustment system of the present invention;

FIG. 5: Perspective view of PSA nitrogen enrichment device and storage container;

FIG. 6 is a perspective view of a storage bag;

[Figure 7] Piping system diagram of the PSA nitrogen enrichment device and storage container,

[Figure 8] Cross-sectional view of a joint that can be connected with one touch,

[Figure 9
] Characteristic diagram of pump operation time and oxygen concentration when the size of the storage container is changed in the atmospheric storage system.

[Explanation of symbols]

1...storage container, 2...external separation membrane module, 3... Internal separation membrane module, 4...Connection tube, 5...Pump, 6...Oxygen sensor.

Claims (3)

[Claims] Claim 1: In a refrigerator consisting of several divided compartments, a storage container with a closed structure with a lid is stored in one corner of the compartment having a temperature range of 3 to 10°C, 1. An atmosphere adjustment storage device comprising: two separation membrane modules; a pump connected to these; and a zirconia solid electrolyte oxygen sensor that sends a control signal to the pump. 2. According to claim 1, the internal air of a removably sealed container with a lid in one room of the refrigerator is nitrogen-enriched air generated by a pressure difference adsorption device comprising an adsorption tower and a compressor. Atmosphere adjustment storage device equipped with connecting pipes that can be connected with one-touch operation. 3. According to claim 1, the air inside the bag made of a polymeric material that is flexible and has excellent gas barrier properties is replaced with nitrogen-enriched air generated by a pressure difference adsorption device, which can be operated with a single touch. Atmosphere adjustment storage device equipped with a connecting pipe that can be connected with.