JP3263523B2 - Environmentally controlled storage of fruits and vegetables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an environmentally controlled method for storing fruits and vegetables for controlling the atmosphere in a storage for a long period of time.

[0002]

2. Description of the Related Art There is a great need for storing fruit vegetables such as tangerines, kabosu, apples and the like for a long period of time from the viewpoint of stable and consistent shipping. Therefore, various freshness techniques have been studied, CO ₂ oxygen concentration (3) essentially corresponding to the oxygen concentration (2) the type of each fruit vegetables in accordance with (1) the type of each fruit vegetables as environmental factors each Low temperature of 0 to 15 ° C depending on the type of fruits and vegetables. (4) Humidity of about 80% of relative humidity. (5) Ethylene, aldehyde, terpene, etc., which are growth promoting factors generated from fruits and vegetables as each fruits grows. Achieved by adjusting the removal of volatile organics. This low-temperature storage is widespread, but a method of adjusting the atmospheric gas by adsorbing and decomposing volatile organic substances generated by wrapping fruits and vegetables in wrapping paper coated with a volatile organic substance decomposer is used. It is about.

[0003]

In order to maintain the freshness during storage of fruits and vegetables, it is necessary to keep the oxygen concentration in the storage at a low concentration of 2 to 4 vol% by removing oxygen from the initial storage amount. In this case, the system is purged with a separate nitrogen generator or stored nitrogen to remove oxygen out of the system (O
₂ pulldown) is required.

Although securing nitrogen for purging is an essential condition for environmentally controlled storage, the ratio of nitrogen consumption to storage cost is extremely large, and reducing the cost of O ₂ pull-down is an extremely important issue. When storage is started, the metabolism of fruits and vegetables consumes oxygen and releases CO ₂ . For this reason, it is no longer necessary to remove oxygen, but rather, it is necessary to supply oxygen suitable for metabolism from outside the system, but this can be easily carried out since air only needs to be supplied to the storage.

At this stage, it is rather important to continuously remove CO ₂ generated by metabolism to the outside of the system. To this end, at present, the storage gas is introduced into the activated carbon adsorption tower to convert CO ₂ into CO _2.
Is adsorbed and removed, and activated carbon saturated with CO ₂ is released by purge regeneration with air from outside the system. C
Since the removal of O _{2 from} the system is performed almost at the atmospheric pressure, the burden is not so large.

However, since nitrogen remaining in the adsorption tower during purge regeneration with air is released to the outside of the system together with CO ₂ ,
In some cases, nitrogen supplementation is required. Activated carbon is a good adsorbent from the viewpoint of avoiding deactivation due to moisture during air regeneration, but the amount of CO ₂ adsorbed is only 1/2 to 1/3 of that of zeolite, and the adsorbent is accordingly reduced. The usage increases.

Volatile organic substances such as ethylene, acetoaldehyde and terpene generated simultaneously with the generation of CO ₂ are aging factors for fruits and vegetables, and oxidative decomposition by halogen oxide supported on activated carbon is often used at present. . In this method, the oxidative decomposition reaction is significantly reduced at a relative humidity of 50% or more, and the relative humidity is reduced to 50% or less to maintain the reaction. Temperature is required, and these pretreatments are rather complicated. Another problem is that halogen oxides are extremely expensive.

[0008] The present invention has been made in view of such circumstances, and as compared with the prior art, the rationalization of the apparatus has been achieved, the equipment cost has been reduced, the power consumption has been reduced, and the simplification of the operation and the ease of maintenance have been ensured. It is an object of the present invention to provide an environmentally controlled storage method for fresh fruits and vegetables.

[0009]

SUMMARY OF THE INVENTION The present invention, oxygen required for keeping the freshness of reservoir crops, CO ₂ concentrations holding, ethyl
In an environmentally controlled storage method for removing volatile organic substances such as ren, acetaldehyde, and terpene, an adsorption tower filled with an adsorbent that adsorbs a substance that inhibits freshness retention during storage of fruits and vegetables is used, and the oxygen concentration in the storage is determined. Under high conditions
Is the gas in the reservoir leading to the adsorption tower adsorbed nitrogen releases flame adsorbable oxygen from the system in the adsorption step, is recovered by leading the adsorbed nitrogen vacuum conditions, CO ₂ concentration in the reservoir
Under high conditions, the adsorption time is longer than the nitrogen adsorption time.
O ₂ is adsorbed and the adsorbed CO ₂ is released to the system under reduced pressure conditions, and the concentration of the ethylene or volatile organic substance is reduced.
Under high conditions , one type of adsorbent that adsorbs volatile organic substances with an adsorption time equal to or longer than CO ₂ adsorption, guides the adsorbed volatile organic substances to a reduced pressure condition, and discharges them out of the system A method for environmentally controlled storage of fruits and vegetables, characterized in that oxygen, CO ₂ , ethylene, and volatile organic substances are removed from the system by changing the adsorption time.

[0010]

The operation of the present invention is as follows. At the start of storage, the storage gas is led to a nitrogen adsorption tower filled with a nitrogen adsorbent to adsorb nitrogen, release oxygen-enriched air from the top of the tower to the outside of the system, and guide the adsorbent adsorbing nitrogen to a reduced pressure to remove nitrogen. The collected gas is returned to the storage and released from the storage to the outside of the system (O ₂ pull-down).

When the storage conditions reach a steady state, the stored fruits and vegetables consume oxygen to release CO _{2 due} to a metabolic mechanism.
Here, if the adsorption time of the adsorption tower extending at least three times during nitrogen adsorption, since CO ₂ is adsorbed low concentration CO ₂ gas flows through from the top, CO ₂ concentration The gas is returned to the reservoir Used to control the rise. The adsorbed CO ₂ is released from the adsorbent by guiding the adsorption tower to a reduced pressure, and is released out of the system.

[0012] The ethylene released simultaneously with the generation of CO _2, acetaldehyde, for strongly adsorbed components than the volatile organic compounds are CO ₂ terpenes such, usually organic substances adsorbed band compared to CO ₂ adsorption zone is quite front portion And the organic matter is released out of the system as a co-adsorbed component as CO _{2 is} eliminated.
If the removal of volatile organic substances is not sufficient when removing only CO ₂ , the adsorption time is further extended and the organic substance adsorption zone is extended to the rear of the tower to remove volatile organic substances during regeneration. Perform

According to this method, one type of nitrogen adsorbent is used for i) O ₂ pull-down, ii) removal of CO ₂ outside the system, and iii) removal of volatile organic substances, which were conventionally performed by separate apparatuses. This is achieved by changing the adsorption time in a single-stage adsorption tower, which achieves i) reduction of equipment cost, ii) reduction of power consumption, and iii) simplification of operation and maintenance by rationalizing the environmental adjustment device. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. Reference numeral 1 in the figure is a storage having a volume of 3 m ³ . This storage 1 has Cabos 1To as an example of fruits and vegetables.
n is stored, and the environmental control conditions of the storage 1 are a temperature of 5 ° C., a relative humidity of 80%, an atmosphere gas composition oxygen 5 vol.
1%, ₅ vol% CO ₂ and 90 vol% nitrogen. Immediately after storage, the temperature in the storage 1 is cooled from room temperature to 5 ° C., and oxygen is removed from the system (O ₂ pull-down).

In the present invention, the flow path 2, the blower 3, the flow path 4,
Atmospheric gas in the storage 1 is transferred to the adsorption tower 6a through the valve 5a.
And reaches the adsorption tower 6a. Here, since 13 × 20 kg of the nitrogen adsorbent 7 is filled in the adsorption tower 6a, moisture, CO ₂ and nitrogen are adsorbed in this order from the front of the adsorption tower 6a, and the valve 8a is admitted from the rear of the adsorption tower 6a. The oxygen-enriched air is discharged out of the system through the valve 9, the valve 9, and the flow path 10.
Since the oxygen concentration at the outlet of the adsorption tower 6a is reduced by the adsorption for about 2.5 minutes, the adsorption step is terminated, and the difference in nitrogen concentration in the storage 1 is to be improved by collecting the adsorbed nitrogen. Even if the pressure in the adsorption tower 6a is reduced, the concentration of the recovered nitrogen does not decrease due to the mixing of unabsorbed oxygen remaining in the adsorption tower 6a.

For this reason, when a part of the recovered nitrogen is purged from the tank 11 through the flow path 12 and the valve 13a in a parallel flow from the front of the adsorption tower 6a, the nitrogen is adsorbed and the oxygen is exhausted to the outside of the system. The concentration of the adsorption tower 6a is significantly improved. In our tests, the recovered nitrogen concentration reached 98 vol% by using about 0.7 m ³ N / h of the recovered nitrogen 1 m ³ N / h for the cocurrent purge. The oxygen-enriched air removed from the adsorption tower 6a by the replacement with nitrogen in the co-current purge step is exhausted from the valve 9 and the flow path 10 to the outside of the system. The adsorption tower 6a containing a high concentration of nitrogen has a valve 14a, a flow path 1
5. Vacuum pump 16 and 1 m ³ N / h of nitrogen are collected in tank 11 by being decompressed to 0.1 atm from flow path 17, and 0.3 m ³ N / h of this is supplied to flow path 15 and valve 18. Through the reservoir 1 and used for purging oxygen in the reservoir 1.
The remaining 0.7 m ³ N / h is used for the co-current purge described above.

When the recovery is completed, the adsorption tower 6a is set to 0.1a
tm, and the process proceeds to the adsorption step as it is, and the pressure of the storage 1 for guiding the raw material gas from the blower 3, the flow path 4, and the valve 5a cannot be maintained, and the air velocity of the adsorption tower 6a increases. As a result, the adsorption zones of water, CO ₂ and nitrogen in the column are disturbed, and the adsorption / separation performance is lowered. In the present invention, in order to avoid this, when the adsorption tower 6a is under reduced pressure, the other adsorption tower 6b
Is in the co-current purging step as shown in the sequence table in Table 1 below, and the valves 8b, 19, and
The outlet gas of the adsorption tower 6b is supplied to the adsorption tower 6a from the rear through the 20a to increase the pressure of the tower. As a result, the step of increasing the pressure of the adsorption tower 6a is performed without affecting the pressure holding of the storage 1 and without disturbing the adsorption zone of the adsorption tower 6a for water, CO ₂ and nitrogen.

When the pressurization is completed, the process returns to the nitrogen adsorption step described first. When the adsorption tower 6a repeats the adsorption-parallel flow purge-decompression-pressure increase, the adsorption tower 6a performs the adsorption-parallel flow purge-decompression-pressure increase with a phase shift of 180 °, so that oxygen from the storage 1 is removed. Purge is performed. In addition, due to the material balance, the amount of gas retained in the capacity-dividing system of the oxygen-enriched air discharged from the valve 9 and the flow path 10 is insufficient, and the pressure in the storage is reduced. The total pressure was detected by 21 and when the pressure became lower than the set pressure, the valve 22 was opened and air was taken in from outside the system to always compensate for the shortage.

[0019]

[Table 1]

Low temperature setting of the storage 1 (5 ° C.),
The condition of setting the nitrogen concentration (95 vol%) is reached in about 100 hours. Thereafter, oxygen in the storage 1 is consumed and CO ₂ is released by respiratory metabolism under the environmental control conditions of Kabos. The replenishment of the oxygen consumption is not so difficult because the oxygen concentration in the storage 1 can be monitored and supplied as a shortage. The removal of CO ₂ is required for selective separation and removal CO _2. In the present invention, the adsorber that produced nitrogen in a two-column four-step configuration in which each column is filled with 13 × 2 Kg is used as it is, and the operation mode is changed to eliminate CO ₂ to the outside of the system. Do.

When the metabolic mechanism of Cabos becomes a steady state and the CO ₂ concentration in the storage 1 exceeds the set CO ₂ concentration of 5 vol%, the atmospheric gas in the storage 1 is adsorbed from the flow path 2, the blower 3, the flow path 4, and the valve 5a. Lead to tower 6a. If the adsorption time at this time is set longer than that during nitrogen production, the CO ₂ adsorption zone expands toward the back of the tower, and nitrogen, which is a weakly adsorbed component than CO ₂ , flows out from the back of the tower (at the same time as oxygen). ), Valve 23, flow path
Return to storage 1 from 24. At this time, Cabos also releases volatile organic substances such as ethylene and acetoaldehyde in addition to CO ₂ , but since these organic substances are components that are more strongly adsorbed than CO _{2 as} much as water, the adsorption zone is located in front of the adsorption tower 6a. Is formed.

When the CO ₂ adsorption zone begins to flow, the valves 5a and 8a are closed, the valve 14a is opened, and the vacuum pump 16
To remove the volatile organic substances such as CO ₂ , ethylene, and acetoaldehyde from the system through the valve 25 and the flow path 26. When the pressure in the adsorption tower 6 a reaches about 0.1 atm, the valves 19 and 20 b To open the adsorption tower 6 in the adsorption process
When the outlet gas b flows from the back of the adsorption tower 6a to the front under reduced pressure conditions, the concentration of CO ₂ and volatile organic matter in the purge gas is lower than that of the inlet gas, so that the CO _{2 is} efficiently removed from the nitrogen adsorbent 7. , Volatile organic substances are removed, and the same is discharged from the valve 25 and the flow path 26 to the outside of the system. By this operation, after removing CO ₂ and volatile organic substances with high efficiency, the valve 14a is closed and the valves 20a and 19 are successively closed.
Is opened, the outlet gas of the adsorption tower 6b is supplied from the rear of the adsorption tower 6a to increase the pressure, and the next adsorption step is performed smoothly.

In the present invention, the adsorption towers 6a and 6b are of a two-column type.
The sequence is configured so that adsorption, decompression, countercurrent purge, and pressure increase operations are performed with a phase shift of 180 ° to continuously remove volatile organic substances such as CO ₂ , ethylene, acetoaldehyde, and terpene. ing. The sequence for removing CO ₂ and volatile organic substances is shown in Table 2 below. In addition,
Reference numerals 5b, 13b, 14b, and 17b in the figure indicate valves.

[0024]

[Table 2]

According to the above-mentioned method, i) O ₂ pull-down, ii) C necessary for environmentally controlled storage by 13x one kind of adsorption tower.
O ₂ removal, iii) ethylene, acetaldehyde, so that the removal of the machine volatile organic terpene or the like is performed.

In the above embodiment, the CO ₂ concentration in the CO ₂ adsorption step was 5 vol%, while the CO ₂ concentration in the outlet was 3 v%.
ol%, the adsorption time was also set so that the adsorption step was completed. At this time, almost ethylene was adsorbed at the outlet of the tower, with 0 ppm at the outlet of the tower, against the ethylene concentration of 10 ppm at the inlet.
The concentration of CO ₂ removed outside the system was 50 vol%, the concentration of ethylene was 80 ppm, and there was almost no loss of nitrogen. Actually, since oxygen supply by respiratory metabolism of oxygen is required, nitrogen is excessive when the desorbed CO ₂ concentration is 20 vol% or more, and there is no nitrogen loss. Depending on the type of stored fruits and vegetables, the removal of volatile organic substances at the same time as the removal of CO ₂ may not be sufficient.However, in this case, the adsorption time is further extended than that of CO _{2 to} remove the organic substances. The organic matter is sufficiently removed only by this adsorption operation.

The nitrogen production according to the above embodiment is 0.04 Kwh for nitrogen production of 1 m ³ N, which is 1/10 of the power consumption of 0.4 Kwh of ordinary PSA-nitrogen and nitrogen production by the membrane method. It is about. Further, power consumption required for CO ₂ removal of 1 m ³ N in CO ₂ removal 0.01K
wh, and volatile organic matter is removed simultaneously with the removal of CO ₂ . As described above, the rationalization of the apparatus is achieved by the environmental adjustment method of the present invention, and the configurations of i) reduction of equipment cost, ii) reduction of power consumption, and iii) simplification of operation and ease of maintenance can be realized.

[0028]

As described in detail above, according to the present invention,
Compared to the past, equipment rationalization has been achieved, equipment cost reduction,
It is possible to provide a method for environmentally controlled storage of fruits and vegetables, which can reduce power consumption and simplify operation and facilitate maintenance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for controlling and storing fruits and vegetables according to an embodiment of the present invention.

[Explanation of symbols]

1 ... storage, 2,4,10,12,15,17,24,26
... flow path, 3 ... blower, 5a, 5b, 8a, 8b, 9, 13
a, 13b, 14a, 14b, 18, 19, 20a, 20b, 22, 23,
24, 25… Valve, 6a, 6b… Adsorption tower, 7… Adsorbent,
11 ... tank, 16 ... vacuum pump, 21 ... pressure gauge, 22 ... valve.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Jun Izumi 5-717-1 Fukahori-cho, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratory (72) Inventor Hiroyuki Tsutaya 5-717 Fukahori-cho, Nagasaki City, Nagasaki Prefecture No. 1 Inside the Nagasaki Research Laboratory of Mitsubishi Heavy Industries, Ltd. (72) Inventor Koichi Araki 1-1-1, Akunouramachi, Nagasaki City, Nagasaki Prefecture Inside the Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (58) Field surveyed (Int. Cl. ⁷ , DB name) ) A23B 7/00-9/00

Claims (1)

(57) [Claims] 1. A method for maintaining the concentration of oxygen and CO ₂ necessary for maintaining freshness of crops in a storage, ethylene and acetaldehyde,
In an environmentally controlled storage method for the removal of volatile organic substances such as terpenes, using an adsorption tower filled with an adsorbent that adsorbs a substance that inhibits freshness retention during fruit and vegetable storage, under conditions where the oxygen concentration of the storage is high is the gas in the reservoir leading to the adsorption tower adsorbed nitrogen releases flame adsorbable oxygen from the system in the adsorption step, is recovered by leading the adsorbed nitrogen vacuum conditions, CO ₂ concentration in the reservoir at high condition, it adsorbed performing adsorption CO ₂ at long adsorption time than the nitrogen adsorption CO
₂ is released to the system under reduced pressure conditions, and under conditions where the concentration of ethylene or volatile organic substances is high.
In this method , the volatile organic substance is adsorbed in an adsorption time equal to or longer than that of CO ₂ adsorption, and the adsorbed volatile organic substance is led to a reduced pressure condition and released to the outside of the system. By changing the time, oxygen, CO ₂ , and
An environmentally controlled storage method for fruits and vegetables, comprising removing ethylene and volatile organic substances out of the system.