JPH0795919B2 - Method for maintaining freshness of plant and apparatus used for implementing the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a plant capable of preserving fruits and vegetables such as fruits and vegetables and flowers and trees stored in storages for a long period of time while maintaining the freshness. And a device used for the method.

[Prior Art] Conventionally, as a technique for long-term preservation of fruits and vegetables, a method of lowering the temperature of fruits and vegetables, a method of lowering the oxygen concentration of atmospheric gas, a method of increasing the CO ₂ concentration of atmospheric gas, etc.
The method of hibernating fruits and vegetables is common.

Recently, it has been found that the storage period of fruits and vegetables can be prolonged by removing ethylene gas, which is a spoilage hormone that promotes maturation and decay of fruits and vegetables, from around the fruits and vegetables in the storage. .

It is considered that the mechanism of decay of fruits and vegetables is that a spoilage hormone composed mainly of ethylene is generated with maturation of the fruits and vegetables, and this spoilage hormone is attracted to further promote maturation. Therefore, particularly for fruits and vegetables stored in a large amount, measures such as lowering the temperature inside the refrigerator as described above are taken so that spoilage hormones are not generated as much as possible, and the spoilage hormones generated are removed from the periphery of the fruits and vegetables. That is effective for long-term storage of fruits and vegetables. Therefore, ventilation is provided so that ethylene gas does not stay around the fruits and vegetables, or an adsorbent such as activated carbon or cristobalite that adsorbs ethylene gas that is a spoilage hormone is installed in the storage, and the air in the storage is circulated to the adsorbent. There has been proposed a technique for removing ethylene gas by the above method (JP-A-06-118144).

[Problems to be Solved by the Invention] However, a large amount of spoilage hormone is continuously generated in a storage that needs to store a large amount of fruits and vegetables. For this reason, it is difficult to remove ethylene gas over a long period of time and at low cost by removing ethylene gas with an adsorbent as in the past.

Further, in the method of removing ethylene gas only by ventilation, it is not possible to leave fruits and vegetables in an atmosphere having a low ethylene gas concentration for a long period of time in a closed space such as in a storage.

The present invention has been made in view of such problems,
Provided are a method for maintaining freshness of a plant, which can remove a large amount of spoilage hormones stably and at low cost over a long period of time, and facilitate long-term storage of plants such as fruits and vegetables, and a device used for the implementation. The purpose is to

[Means for Solving the Problems] A method for maintaining freshness of a plant according to a first aspect of the present invention is a catalyst that oxidizes ethylene to produce at least water, and a gas containing ethylene released by plants in a storage and heating. It is characterized in that the regenerated gas whose temperature is raised is forcibly fed alternately.

A plant freshness maintaining apparatus according to a second aspect of the present invention includes a case provided with a gas inlet and a gas outlet, and a fan and a heater arranged in the case and arranged in parallel in a direction from the gas inlet to the gas outlet. And a catalyst, and control means for turning on and off the heater each time a predetermined off time and a predetermined on time of the heater elapse, and the catalyst oxidizes ethylene to generate water. And introducing ethylene-containing gas released from plants in the storage into the case by the fan through the inflow port, passing the catalyst, and then supplying the gas into the storage from the exhaust port. .

A plant freshness maintaining apparatus according to a third aspect of the present invention includes a catalyst that oxidizes ethylene to produce water, a driving unit that rotationally drives the catalyst around its central axis, and a part of a region where the catalyst exists. The gas in the plant storage is supplied to the processing zone provided, and the inside air supply means for returning the gas inside the storage to the inside of the processing zone by passing through the catalyst portion of the processing zone, and to the rest of the area where the catalyst exists. An outside air supply means for supplying a gas outside the storage to the provided regeneration zone and passing the outside gas through the catalyst portion of the regeneration zone to the outside of the storage; and a storage for supplying to the regeneration zone. And a heating means for heating the outside air.

[Operation] In the present invention, ethylene, which is a putrefactive hormone, is stably oxidatively decomposed for a long period of time using a catalyst at room temperature or low temperature.

Generally, iron-manganese-based, copper-manganese-based, or copper-zinc-based catalysts are known as room-temperature-reactive catalysts for hydrocarbon gases such as ethylene, but these catalysts react ethylene gas in an air balance. When decomposed, it decomposes into water and carbon dioxide. The water generated here is partially adsorbed on the catalyst to block the active groups of the catalyst, resulting in water deactivation of the catalyst. Therefore, from the viewpoint of catalyst life, use at room temperature has been restricted.

With respect to the water deactivation phenomenon of the catalyst, the inventors of the present application obtain the original catalytic reaction again by heating the catalyst itself or circulating a high temperature gas to separate the adsorbed water. From this viewpoint, the catalyst was made to be usable continuously for a long time.

That is, normal temperature or low temperature air containing ethylene is supplied to a predetermined catalyst layer to oxidize and decompose ethylene, and water, which is one of its reaction products, is adsorbed to the catalyst after a certain period of time and the catalytic action is lowered. Before heating, the heated and heated air is supplied to the catalyst for a predetermined period of time, and the hot gas removes the moisture adhering to the catalyst. In this way, the catalytic action is restored, so that the ethylene-containing gas is again fed to the catalyst to decompose ethylene. At least locally, by alternately passing such an ethylene-containing gas and a regenerated heating gas through the catalyst portion, the ethylene gas can be continuously controlled to have a low concentration for a long period of time.

According to the device according to the second aspect of the present invention, such a removal of ethylene gas is performed by forming a flow of air in the case from the air inlet of the case through the catalyst to the air outlet in the case by the fan, This can be done by controlling on / off. That is, when the control means first turns off the heater for a predetermined period and allows the air containing ethylene gas to pass through the catalyst as it is, the catalyst decomposes the ethylene gas to generate water. Next, since the resolution of ethylene gas begins to decrease as the water content advances, the heater is turned on by the control means to heat the air from the air inlet after a certain period of time, and then the catalyst is passed through the catalyst. The attached water is removed from the catalyst. By repeating the on / off of the heater in this manner, the catalyst can be continuously and stably operated for a long period of time to decompose the ethylene gas in the internal gas.

On the other hand, in the device according to the third invention of the present application, while the catalyst is rotated around its central axis, the ethylene-containing gas in the storage is fed to the treatment zone and the warmed regeneration gas is fed to the regeneration zone. To pay. As a result, the catalyst portion that has been passed through the treatment zone and used for the decomposition of ethylene has its moisture removed by the hot gas while passing through the regeneration zone. In this way, in this apparatus, the gas in the cold storage can be continuously processed.

[Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings.

In the example method of the present invention, ethylene is decomposed by passing it through a catalyst at room temperature without heating the ethylene-containing gas in the storage storing fruits and vegetables.

BACKGROUND ART Conventionally, a technique is known in which a spoilage hormone-containing gas containing ethylene as a main component is heated to several hundred degrees and then passed through a catalyst to decompose ethylene. However, this technique cannot be directly applied to maintain the freshness of fruits and vegetables. As described above, when storing fruits and vegetables, it is also important to prevent spoilage hormones from being produced from the fruits and vegetables, and the suppression of the generation of ethylene gas itself and the removal of the generated ethylene gas are combined. It prevents the decay of fruits and vegetables and enables long-term storage. Therefore, it is necessary to store the fruits and vegetables themselves in a low temperature range, and it is extremely difficult to raise the temperature of the ethylene-containing gas to react with the catalyst from the viewpoint of processing cost and system configuration.

Therefore, in the method of this example, the ethylene-containing gas in the storage is passed through the catalyst at room temperature. In this case, there is a problem that a part of the gas generated by the decomposition of ethylene gas becomes water, and this water adheres to the catalyst to deteriorate the decomposition performance of ethylene gas. Therefore, even if the ethylene-containing gas at room temperature is continuously passed through the catalyst, it is difficult to stably process a large amount of gas for a long period of time.

In the method of this example, in order to eliminate such a difficulty, the heating temperature rising gas is applied to the catalyst just before the decomposition performance of the catalyst is deteriorated by the adsorption of water to the catalyst, and the adsorbed water is separated from the catalyst. Regenerate the catalyst. Then, after the catalyst is regenerated, the spoilage hormone-containing gas in the storage is passed through the catalyst again to decompose the ethylene gas in the storage. Then, by passing such a spoilage hormone-containing gas and passing the heated regenerated gas alternately over a predetermined period, respectively,
The catalyst maintains stable decomposition performance for a long period of time, the ethylene concentration of the gas in the storage is maintained at an extremely low value, and it is stored at room temperature or low temperature without giving a large heat load to the storage. It becomes possible.

As described above, as a means for alternately passing the spoilage hormone-containing gas to be treated and the regenerated heating gas with respect to a specific portion of the catalyst, the stationary catalyst is treated intermittently and alternately. The gas and the regeneration gas may be supplied, or the catalyst may be alternately moved to the processing gas supply region and the regeneration gas supply region.

As the catalyst, a catalyst that has excellent ethylene decomposition performance at room temperature and has stable performance in a cycle including a regeneration process is used. Such catalysts include copper, manganese or oxides thereof, or one or a mixture of two or more thereof. This type of catalyst is extremely superior to other known catalysts such as iron-based or zinc-based catalysts in decomposition performance at room temperature and regeneration performance by water desorption.

Further, the larger the amount of the catalyst used, the greater the effect of the ethylene decomposition.

Further, for the ethylene-containing gas forcibly fed to the catalyst, it is preferable that the air volume is large because the decomposition amount of the spoilage hormone increases, but if the air volume is too large compared to the internal volume,
Since it is a factor that accelerates the surface drying of fruits and vegetables and adversely deteriorates the quality of fruits and vegetables, it is necessary to maintain the proper air volume according to the variety of fruits and vegetables.

Next, the apparatus used for carrying out the method of the present invention will be specifically described.

FIG. 1 is a schematic cross-sectional view of a freshness maintaining apparatus showing an embodiment in which the present invention is applied to maintain freshness of fruits and vegetables stored in a small storage.

In this device, an air (gas) intake port 2 and an air discharge port 3 in the storage are formed at both ends of the case 1,
A filter 4 is installed in the case 1 near the intake port 2, and a catalyst 7 is installed in the case 1 near the discharge port 3. A fan 5 and a heater 6 are arranged between the filter 4 and the catalyst 7.

This freshness preservation device is a commercial frequency power outlet (AC
The fan 5 is connected to 100 V) and supplied with electric power, and the fan 5 is continuously operated after the power is turned on to form an air flow in the case 1 with an air volume of 60 m ³ / hour, for example. Heater 6
Are intermittently driven by a timer (not shown) such that the catalyst activity is not lowered, for example, it is operated for 20 minutes and then for 3 minutes. The capacity of this heater is, for example, 800 W, and the amount of air passing through is approximately 80
Raise to a temperature of ° C.

The catalyst 7 is usually used in the form of pellets, but in order to process a large amount of gas with high efficiency as in the present invention, the pressure loss is small, and the contact reaction with the flowing gas is performed well. It is preferable to form the honeycomb shape. For example,
When the catalyst 7 is formed into a honeycomb shape having about 500 through holes per square inch, the pressure loss is 1/10 or less of that of the pellet-shaped catalyst. Therefore, the air blown by the fan 5 can be performed with low power. Further, in the catalyst 7, the total content of copper, manganese and its oxide is 70% by weight, and the balance is a binder component and impurities. The catalyst 7 has, for example, a width of 60 mm, a length of 120 mm, a height of 50 mm, and a volume of 360 cc.

In the freshness maintaining device thus configured, the fruits and vegetables are stored and the device is loaded into a storage cooled by an appropriate cooling device, and the power is turned on to start the fan 5. Then, the air in the storage is taken into the case 1 through the intake 2, and the air in the storage is filtered by the filter 2
After the dust or dust is filtered by, it passes through the heater 6 and the catalyst 7, and is then discharged from the discharge port 3 into the storage and returned. In this way, the fan 5 forces the inside air to circulate through the filter 4, the heater 6, and the catalyst 7. The heater 6, for example, waits for 20 minutes, during which the air in the chamber is acted on by the catalyst 7, and ethylene gas, which is a putrefactive hormone contained in the air, is decomposed into water. This moisture gradually adheres to the catalyst.

Then, after 20 minutes have elapsed, the heater 6 is turned on by the timer operation, and the air passing through the inside of the case 1 is heated by the heater 6 to, for example, 80 to 90 ° C. When this high temperature air passes through the catalyst, the water adhering to the catalyst 7 is removed and the catalyst 7 is regenerated. Next, for example, after the lapse of 3 minutes, the energization of the heater 6 is stopped. While the heater is energized, high-temperature air is discharged from the discharge port 3 into the chamber, but the energization time of the heater 6 is short and the amount of air discharged into the chamber during this period is extremely small compared to the total volume of the chamber. Therefore, the discharge of the high temperature air does not reach the temperature of the inside of the refrigerator which is constantly cooled.

Next, in the next 20 minutes, the ethylene gas-containing air in the storage passes through the catalyst 7 at the internal temperature, and the contained ethylene gas is decomposed. By repeating the intermittent operation of the heater 6 as described above, the amount of ethylene gas in the refrigerator is decreased or the ethylene gas concentration in the refrigerator is maintained at an extremely low value. Therefore, the fruits and vegetables in the refrigerator are always kept fresh.

Actually, using the apparatus shown in FIG. 1, the operating conditions of the heater and the specifications of the processing air volume of the fan were set to about 60% as described above.
This device was installed in a storage container having an internal volume of m ³ and adjusted to a temperature of 3 ° C. by an appropriate cooling device. Then, after introducing ethylene gas into the chamber to a concentration of 100 ppm and operating the device, the ethylene gas concentration decreased to 20 ppm in about 1 hour, and 0.05 ppm after 5 hours.
It dropped to below.

By the way, for example, apples are refrigerated at the production site and are stored for a long period of time in a CO ₂ gas-rich atmosphere, but they are delivered to the site based on demand.
Conventionally, there has been a problem that unless a refrigerated container vehicle is used for this transportation, maturation occurs rapidly in the middle of the transportation and the spoilage rate becomes high. Therefore, the device of the present embodiment described above is loaded in a closed normal (not refrigerated) container vehicle,
When we attempted to transport apples, their spoilage rate was below the allowable limit, and they were fully usable. In addition,
At the time of normal transportation, the ethylene concentration is confirmed to be in the range of several ppm to several tens of ppm, but in the case of this example, the detection limit of the detector tube was kept at the level of 0.2 ppm or less. In this way, the economic merit of not using a refrigerated container vehicle is enormous.

Next, an embodiment in which the present invention is applied to maintain the freshness of fruits and vegetables stored in a large storage will be described with reference to FIG. In this example, catalytic decomposition of spoilage hormone at room temperature and removal of adsorbed water are carried out in parallel.

That is, a cylindrical catalyst fitted in a cylindrical casing
Similar to the first embodiment, 10 has a honeycomb shape, and is driven to rotate around the central axis by a motor 11 with the direction of extension of the through hole aligned with the central axis. The rotor-shaped catalyst 10 has, for example, a diameter of
The length is 600mm and the length is 20mm. The housing (not shown) of the device has a filter 12 at the inlet for taking in the air in the cabinet.
The inside air filtered by this filter 12 is supplied to the treatment zone 10a of the rotor-shaped catalyst 10 by the inside air blower 13 via the pipe 14 and after passing through this treatment zone 10a. , Outlet 1 provided in the housing
It is guided to the container 5 and is supplied to the inside of the refrigerator through the discharge port 15.
The internal air circulation amount by the blower 13 is, for example, 1200
m ³ / hour.

On the other hand, a filter for outside air provided in the device housing
Air outside the storage is supplied to 16 through an appropriate pipe (not shown). Then, the outside air filtered by the filter 16 is blower 17 for outside air.
As a result, it is supplied to the regeneration zone 10b of the rotor-shaped catalyst 10 via the pipe 18. The outside air circulation amount by the blower 17 is, for example, 200 m ³ / hour. A heater 19 having a capacity of, for example, 15 KW is provided in the middle of the pipe 18, and the outside air supplied to the regeneration zone 10b is heated by the heater 19 to raise the temperature to about 80 ° C. There is. The hot air that has passed through the regeneration zone 10b is guided to the outside air discharge port 20 provided in the housing, and is discharged from the discharge port 20 to the outside of the storage via an appropriate pipe (not shown).

The area ratio between the treatment zone 10a and the regeneration zone 10 in the rotor-shaped catalyst 10 is, for example, 6: 1.

In the freshness maintaining device configured as described above, the rotor-shaped catalyst 10 is constantly driven by the motor 11 to rotate in one direction at a rotation speed of 6 rph, for example. Then, after the inside air is filtered by the filter 12 by the blower 13, it is circulated and supplied to the treatment zone 10a of the catalyst 10 at a flow rate of, for example, 1200 m ³ / hour. The room temperature air at room temperature passes through the catalyst 10 in the treatment zone 10a, whereby the contained ethylene gas is decomposed and water is produced. This moisture adheres to the catalyst 10, but the portion to which the moisture adheres due to the rotation of the rotor-shaped catalyst 10 rotates to the regeneration zone 10b, and the moisture is removed from the catalyst 10 by the passage of high temperature air in this regeneration zone 10b. It
This high-temperature air is taken into the device from the outside through the intake 16, and is heated by the heater 19 to, for example, about 80
After being heated to ℃, it is supplied to the regeneration zone 10b. As described above, this high-temperature air is used to regenerate the catalyst portion to which moisture has adhered in the treatment zone 10a, and then the relatively high-temperature air containing this moisture is guided to the outside of the refrigerator via the outlet 20, Released to the outside.

In this embodiment, the regeneration air is not discharged into the refrigerator but is discharged outside the refrigerator, so that the influence of the regeneration air on the temperature and humidity inside the refrigerator is extremely small. Moreover, while the catalyst 10 is rotated, the decomposition of the ethylene gas and the moisture removal regeneration are performed in parallel, so that the ethylene gas can be continuously decomposed.

As a result of purifying the inside of a refrigerating storage room with an internal volume of 8000 m ³ for storing mandarin oranges under the above-mentioned operating conditions by using the freshness maintaining device shown in FIG. It fell to 1/5.

The catalyst used in the present invention may be a room temperature oxidation type catalyst as described above, but the most efficient decomposition at room temperature and low humidity was obtained is copper manganese or its oxide or It is one kind or a mixture of two or more kinds.

[Effect of the Invention] According to the present invention, a spoilage hormone mainly composed of ethylene generated in the storage of fruits and vegetables is decomposed under the action of a catalyst, and the produced water is removed from the catalyst by heating gas. Can be maintained at an extremely low value, and fruits and vegetables can be stably stored for a long time.

[Brief description of drawings]

FIG. 1 is a sectional view showing a freshness maintaining device according to a first embodiment of the present invention, and FIG. 2 is a perspective view showing a freshness maintaining device according to a second embodiment of the present invention. 4,12,16; Filter, 5; Fan, 6,19; Heater, 7,10; Catalyst, 13,17; Blower

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B01J 23/889 23/94

Claims (3)

[Claims] Claims: 1. A catalyst that oxidizes ethylene to produce at least water is forcedly and alternately fed with a gas containing ethylene released from plants in a storage and a regenerated gas heated and heated. A method for maintaining the freshness of plants characterized by. 2. A case provided with a gas inlet and a gas outlet, a fan, a heater and a catalyst arranged in the case and arranged in parallel in a direction from the gas inlet to the gas outlet, and the heater. Control means for turning on and off the heater each time a predetermined off time and a predetermined on time elapse,
And the catalyst is one that oxidizes ethylene to produce water, and a gas containing ethylene released by the plants in the storage is introduced into the case through the inflow port by the fan, and the catalyst is An apparatus for maintaining freshness of plants, which is characterized in that after passing through, it is supplied from the outlet into the refrigerator. 3. A catalyst for oxidizing ethylene to generate water, a driving means for rotationally driving the catalyst around its central axis, and a plant storage in a treatment zone provided in a part of a region where the catalyst is present. The internal storage air supply means for supplying the internal gas and returning the internal storage gas to the inside of the storage chamber by passing through the catalyst portion of the processing zone, and the storage space in the regeneration zone provided in the remainder of the area where the catalyst exists. And a heating means for heating the outside air to be supplied to the regeneration zone. An apparatus for maintaining freshness of a plant, comprising: