JPH0441315A - storage device - Google Patents

Abstract

PURPOSE:To enable automatic adjustment for maintaining a gas density ratio stably in a storage shed at a set density ratio, by operating an air supply means and an adjusting air generating unit on the basis of the detection signals of oxygen and carbon dioxide detecting means. CONSTITUTION:When O2<=2% or CO2>=5% is detected in a closed storage shed 2, a compressor 17 and a dryer 18 in an air supply unit 4 are started. An air supply valve 14 is opened to supply compressed air from the unit 4 into the storage shed 2, and this air supply is continued until reaching O2>=4%. Upon reaching O2>=4%, the valve 14 is closed to stop air supply. Unless a CO2 density ratio in the storage shed is CO2<=3%, an adjusting air generating unit 3 is operated to open a takeoff valve 43, and an O2 density ratio in adjusting air from a nitrogen tank 33 is detected by an O2 sensor 44. An adjusting air generating cycle is then repeated in the unit 3 until detecting O2>=4%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a storage device, and more particularly to a storage device in which a storage chamber is filled with a gas to maintain the freshness of stored items.

2. Description of the Related Art Fresh foods such as vegetables and fruits are generally stored in storage devices to maintain their freshness until they are shipped.

In addition, for long-term storage of these stored items, the inside of the storage room must be kept at a low temperature to prevent the stored items from freezing, making them inert, lowering the oxygen concentration in the atmosphere to the minimum necessary, and adding carbon dioxide to suppress respiration. It is considered the best way to do this, and this type of research has been ongoing recently. A storage method that utilizes this phenomenon is called a CA (controlled atmosphere or chondral atmosphere) storage method.

In a storage device using this method, the inside of the storage warehouse is maintained at the minimum necessary oxygen (02), and the necessary maximum amount of carbon dioxide gas (C○2 gas) is put in, and the rest is filled with nitrogen gas (N, gas). ) etc. must be maintained with inert gas.

In this way, in the storage device, first, the O of the storage.

N2 gas or CO□ gas is injected into the warehouse to reduce the gas concentration, but in conventional storage devices, CO□ gas and N2 gas are stored in respective cylinders, or propane gas is used. This is produced by combustion, and the storage is connected with piping, and a valve device is installed in the middle of the piping.
By opening and closing this valve device, CO, gas + Nt gas was supplied into the storage.

Also, depending on the type of fruits and vegetables, the optimal O,
Since the ratio of gas to COx gas, N, and gas is determined, it is necessary to always keep it constant. However, as mentioned above, since the stored material respires, the amount decreases over time. Gas is consumed, CO2 gas is generated, and the gas concentration ratio inside the refrigerator changes. Therefore, during the storage period, it is necessary to monitor changes in the gas concentration inside the warehouse and adjust it so that it always remains constant.

When CO2 gas increases due to the respiration of fruits and vegetables, a CO8 adsorbent is used to remove the CO2 gas.

Problems to be Solved by the Invention However, in the conventional storage device described above, a gas cylinder or a propane gas combustion device is inevitably required to store the stored items. As the number of cylinders increases, a larger installation space is required, and furthermore, it is troublesome to manage the cylinders, such as checking the remaining amount of gas. In particular, when the gas in the cylinder is used up, the cylinder needs to be replaced, and the replacement work is troublesome. In addition, the propane gas combustion method requires the management of propane gas, and there is a risk of fire. It was also necessary to replenish CO2 adsorbent.

An object of the present invention is to provide a storage device that solves the above problems.

Means for Solving the Problems The present invention provides a storage in which oxygen and carbon dioxide are maintained at a predetermined concentration ratio in order to maintain the freshness of stored items; an oxygen concentration detection means for detecting the oxygen concentration in the storage; a carbon dioxide concentration detection means for detecting the carbon dioxide concentration; an air supply means for supplying air to the storage; a modified air generation unit for generating air with a low oxygen concentration as modified air; an oxygen concentration detection means and a carbon dioxide concentration detection means; Based on the detection signal from the detection means, the air supply means and the modified air generation unit are operated to supply atmospheric air or the modified air into the storage so that the oxygen concentration and carbon dioxide concentration within the storage are maintained at predetermined set values. and a supply concentration control means.

Operation In the present invention, when the ratio of the 02 concentration or the C02 concentration in the storage chamber deviates from the set value, the air supply means and the modified air generation unit are activated. Atmospheric air (0, 21% concentration) is supplied into the storage from the air supply means to increase the 02 concentration, and modified air (N2 gas including O2 gas) is automatically supplied from the modified air generation unit. Ru. Therefore, the concentration inside the storage room is increased to 0□ in a short time, and when the CO2 concentration becomes high, the C○2 concentration is increased by supplying corrected air.
The gas is exhausted and the CO2 concentration is adjusted to a set value, and the gas inside the warehouse is maintained at a concentration ratio suitable for long-term storage of stored items.

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a configuration diagram of a storage device 1 which is an embodiment of the present invention. Roughly speaking, the storage device 1 is a storage warehouse 2. Modified air generation unit 3. Air supply unit 4. Gas concentration detection unit5. It is composed of a programmable controller (hereinafter simply referred to as a controller) 6.

The storage 2 stores fresh foods such as fruits and vegetables therein, and is configured so that the inside is maintained at a low temperature such that the stored items do not freeze by a refrigeration device (not shown).

In addition, the storage 2 is configured to be airtight when the door for putting in and taking out stored items is closed, and there is also a fan (
(not shown) is provided so that the inside air can be stirred. Inside this storage 2, there is an 02 sensor at 7°C.
O, a sensor 8 is provided.

9 is a modified air supply pipe (hereinafter referred to as modified air pipe) connected to the modified air generation unit 3; 10 is an oxygen supply pipe 9 (hereinafter referred to as O2 pipe) connected to the air supply unit 4; and 11 is a discharge pipe. Each is connected to the storage 2 by piping. N, pipe 9 has a throttle valve 12. A three-way solenoid valve 13 is provided. The modified air from the modified air generation unit 3 is throttled to a predetermined flow rate by the throttle valve 12, and then
3 is supplied into the storage 2 when it is energized. Also, 02
The piping 10 has an air supply valve 14. A throttle valve 15 is provided, and air from the air supply unit 4 is supplied into the storage 2 via the throttle valve 15 when the air supply valve 14 is opened.

The modified air generation unit 3 is a gas separation device that is supplied with air, which is mainly a mixed gas of nitrogen and oxygen, and separates the air into nitrogen and oxygen, which are modified air. This modified air generation unit 3 is connected to an air supply unit 4 via a pipe 16.

The air supply unit 4 includes a compressor 17 and a dryer 18 that dries the compressed air from the compressor 17. The dryer 18 is then connected to the pipe 16.10 and supplies dry compressed air to the storage 2 and the modified air generation unit 3.

Here, the configuration of the modified air generation unit 3 will be explained.

In the figure, 21.22 is the 1st. In the second adsorption tank, each adsorption tank 2
Molecular sieve carbons 21A and 22A (indicated by matte finish in the figure) are filled in the inside of each of the sieves 1 and 22 as adsorbents for adsorbing oxygen.

Pipes 23 and 24 discharge gas from the adsorption tanks 21 and 22 during desorption, and are connected to a common discharge pipe 25, respectively, and the discharge pipe 25 discharges the adsorbed gas (in this example, adsorbed oxygen). It is designed to be discharged. Gas exhaust valves 26 and 27, which are electromagnetic valves, are provided in the middle of the pipes 23 and 24, respectively, for alternately exhausting the desorbed gas in the adsorption tanks 21 and 22 every half cycle.

On the other hand, 28.29 is an extraction pipe for taking out nitrogen from the adsorption tank 21.22, and 30 is an extraction pipe connected to each of the pipes 28 and 29. Take-out valve 31.3 consisting of a solenoid valve that opens when
2 are provided respectively. Further, the extraction pipe 30 is connected to a modified air tank 33 that stores the generated modified air (N2 gas containing low concentration 02 gas).

Further, a pressure reducing valve 38 is disposed in the pipe 16, and an air supply valve 41.42 is disposed in a pipe 39.40 communicating with the pipe 16 and connected to the adsorption tank 21.22.

36 is a pipe that communicates between the adsorption tanks 21 and 22, and 37 is a pressure equalization valve consisting of a solenoid valve provided in the middle of the pipe 36. The valve is opened for a short time to equalize the pressure between each adsorption tank 21 and 22.

A modified air pipe 8 that supplies the modified air generated by the modified air generation unit 3 to the storage 2 is connected to the modified air tank 33, and in the middle of the modified air pipe 8 is a take-out valve 43 made of a solenoid valve. , an 02 sensor 44 that detects the 02 concentration contained in the modified air from the modified air tank 33
It is arranged.

The gas concentration detection unit 5 is a 0□ concentration meter 45°4s, Co
It has a densitometer 47. Each 02 concentration meter 45.46. C.O.
2 concentration meter 47 is the 0□ sensor 44.7. It is connected to the cot sensor 8, and outputs whether or not the concentration is within the set range based on detection signals from each sensor 44, 7.8. The signal output from the gas concentration detection unit 5 is input to the controller 6. The controller 6 controls the modified air generation unit 3 based on the detection signals from each sensor. While operating the air supply unit 4, the three-way solenoid valve 13
．． By switching the air supply valve 14, the 02 concentration in the storage 2,
It has a concentration control means 6A that controls opening and closing of each electromagnetic valve so that the COt concentration becomes a predetermined value.

The controller 6 also includes a start switch 48 for the storage device 1 and an 02 concentration setting switch 49 for setting the 02 concentration in the storage 2. A CO1O1 concentration setting switch 50 for setting the CO2 concentration is connected.

Next, the operation of the storage device 1 having the above structure will be explained with reference to FIG. 2.

First, O8 concentration setting switch 49. Operate the C○, concentration setting switch 50 to set the ○, concentration, and Cot concentration in the storage 2. In this example, the concentration is 0, and the concentration is 2%≦0. ≦
4%, and the CO2 concentration is set to 3%≦CO2≦5%.

Here, when the operator turns on the start switch 48, the controller 6 executes the process shown in FIG. 2.

In FIG. 2, when the start switch 48 is turned on, the dryer 18 and the compressor 17 are started simultaneously (step Sl). Subsequently, the operation of the modified air generation unit 3 is started, and the compressed air generated by the compressor 17 is dehumidified by the dryer 18 and then sent to the adsorption tank 21 via the pressure reducing valve 38.
or 22 (step S2).

In the modified air generation unit 3, each electromagnetic valve is controlled to open and close as described above, and the operation of the nitrogen generation cycle is executed. At this time, the modified air generation unit 3 generates 0. To lower the concentration in a short time, press the concentration setting switch 4.
9.50 is ignored to produce the gas with the lowest 02 concentration, that is, high purity nitrogen gas. In this way, nitrogen tank 3
3, high purity nitrogen gas is stored.

Before starting the device, the storage 2 is filled with air (02 concentration approximately 21%), so the take-out valve 43 is opened, the three-way solenoid valve 13 is energized, and the modified air (02 concentration approximately 21%) is discharged from the modified air tank 33.
low concentration oxygen) is supplied into the storage 2.

The gas concentration ratio in the storage 2 is constantly detected by the O2 sensor 7 and the CO2 sensor 8, and the detection signals from the O2 sensor 7 and the CO2 sensor 8 are detected by the O7 concentration meter 46. CCL concentration meter 4
7 is output. The above operation of the modified air generation unit 3 is continued until the inside of the storage 2 becomes O, ≦4% (02 concentration upper limit value) by the 02 sensor 7 (step S4). After a while, when the oxygen concentration in the storage 2 reaches 02≦4%, the extraction valve 43 is closed to stop the supply of nitrogen gas from the modified air generation unit 3 (step S5), and then the modified air generation unit 3 (step 36). Subsequently, the compressor 17 and the dryer 18 are stopped (step S7).

When fresh foods such as fruits and vegetables are stored in the storage 2, the oxygen concentration in the storage 2 decreases over time due to the respiration of the fresh foods, and conversely, carbon dioxide increases. Therefore,
In step S8, the gas concentration ratio in the storage 2 is reduced to 0.0 due to the above-mentioned respiration. ≦2% (02 concentration lower limit) or COz≧
Monitor whether the concentration has reached 5% (C○2 concentration upper limit value).

0, concentration that can maintain the freshness of fresh foods for a long time.

CO2 concentration varies depending on the type of food, or there is an optimum value within a certain range. However, if the sealed storage 2 is left as it is, the respiration will cause 0. The concentration has decreased to nearly the lower limit of 2%, and if left as it is, it will reach 0. If the concentration becomes too low, the freshness of the food will decrease.

Therefore, in Stainless steel S8, 02≦2% or 60
When it reaches 225%, the compressor 17 and dryer 18 of the air supply unit 4 are activated (step S9).

Then, the air supply valve 14 is opened to supply compressed air from the air supply unit 4 into the storage 2. This process is continued until the gas concentration ratio in the storage 2 reaches 0□≧4% (upper limit) (step SIO, 5ll).

Note that in step Sll, the air in the atmosphere is dehumidified and introduced into the storage 2. Air contains approximately 21% oxygen and 0.03% carbon dioxide.

Nitrogen makes up most of the rest. Therefore, by supplying atmospheric air into the storage 2, the O6 concentration ratio within the storage 2 can be increased in a short time. in this way,
02 Highly concentrated air is supplied to the storage 2, where the CO2 concentration is high due to the respiration of the stored materials.
This is to prevent the gas inside from being discharged to the outside as much as possible.

Then, in step SIO, when ≧4% is reached, the air supply valve 14 is closed to stop the air supply (step 512).

Next, if the CO2 concentration ratio in the storage 2 is not 60253% (lower limit value) in step S13, the modified air generation unit 3 is started operating again (step 514).
. In step S15, the take-out valve 43 is opened and the O2 sensor 44 detects 0.0% of the modified air from the nitrogen tank 33. A concentration ratio is detected. In the PSA type modified air generation unit 3, the N2 concentration in the modified air tank 33 decreases while the unit is stopped, and the 02 concentration is high at the beginning of operation.

Therefore, the modified air generation cycle is repeated several times in the modified air generation unit 3 until 02≧4% (upper limit) is detected in step S15. During this time, the three-way solenoid valve 13 is demagnetized, and the gas in the modified air tank 33 is discharged into the atmosphere via the three-way solenoid valve 13. As a result, when the nitrogen concentration ratio of the gas from the modified air tank 33 increases and reaches 02≧4%, the three-way solenoid valve 13 is energized.
The modified air (low-concentration 0□ gas, in this example, O, N gas containing a concentration of 4%) from the nitrogen tank 33 is supplied to the storage 2 (step 516).

The supply of modified air in step S16 is continued until the carbon dioxide in the storage 2 becomes CO, ≦3%, and the 02 concentration is reduced to 4%.
(step 51).
7).

In step S17, modified air (in this embodiment, N2 gas containing 4% 02) is supplied into the storage 2, and the CO concentration is relatively reduced. And the inside of storage 2 is 00
When it reaches 153%, the take-out valve 43 is closed to stop the supply of modified air to the storage 2 (step 318).

Subsequently, the modified air generation unit 3 is stopped (step 519).

Furthermore, the compressor 17. Stop the dryer 18 (
After step 520), the process returns to before step S8. Therefore, the processes of steps 38 to S20 are repeated thereafter.

Also, when co≦3% (lower limit) in step S13, the process moves to step S20 and the compressor 17. The dryer 18 is stopped, and then the process returns to step S8 and the processes of steps 88 to S20 are repeated.

Therefore, due to the respiration effect of the stored material, the concentration of 0□ is lower than the lower limit of 2%.
When the CO2 concentration drops further, or when the CO2 concentration exceeds the upper limit of 5%, the air (approximately 21%) or the storage
and supplies modified air (N2 gas with low concentration of 02 gas) to the storage 2 when the Co2 concentration is not less than 3%. Therefore, by repeating the processes of steps 88 to S20, the gas in the storage 2 always maintains the predetermined concentration ratio (2%≦0.≦4%, 3%≦) set by the concentration setting switch 49.50. co, ≦5%). Therefore, the stored foodstuffs can be stored stably for a long time in the storage 2.

Further, according to this embodiment, since there is no need to prepare a cylinder for each gas, there is no need for troublesome operations such as checking the remaining amount of gas in the cylinder or replacing used cylinders. Particularly in the case of a large storage facility, the apparatus of the present invention is advantageous from this point of view as there is no need for space for installing a large number of cylinders and for managing them.

Furthermore, in this embodiment, to control the CO7 concentration, there is no need to burn propane gas or use a CO7 absorbent, etc., as in the past, and the concentration can be easily controlled. There is no need for troublesome work such as replenishing absorbent, and there is no risk of fire.

In addition, in the above embodiment, the gas concentration ratio in the storage 2 is set to 2%≦
02≦4% and 3%≦C○2≦5%, but the present invention is not limited to this, and may be changed as appropriate depending on the type or amount of fruits and vegetables stored in the storage 2.

Effects of the Invention As described above, the storage device according to the present invention supplies air from the atmosphere to increase the O1 concentration in the storage in a short time when the oxygen concentration in the storage becomes lower than the set value due to the breathing action of the stored material. In addition, when the CO concentration exceeds the set value, nitrogen gas with a low oxygen concentration generated by the modified air generation unit can be supplied to reduce the carbon dioxide concentration without reducing oxygen. I can do it. Therefore, the gas concentration ratio in the storage room can be automatically adjusted to maintain a preset concentration ratio stably so that stored products such as fruits and vegetables can be stored for a long time. Since air with an oxygen concentration (corrected air) is also used, the gas concentration can be easily controlled.

Furthermore, unlike conventional oxygen cylinders, there is no need for an oxygen cylinder, and troublesome operations such as checking the remaining amount and replacing cylinders can be avoided. In addition, in the case of a large storage room, a large number of cylinders are required, but since these are unnecessary in the present invention, there is no need to secure installation space for a large number of cylinders, and there is no need for troublesome cylinder management.

In addition, to generate COl, there is no need to burn propane gas or use a CO3 adsorbent as in conventional methods, eliminating the need to manage propane gas cylinders or replenishing CO adsorbent, and further reducing the risk of fire. It has the following features:

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of a storage device according to the present invention, and FIG. 2 is a flowchart for explaining processing executed by a programmable controller. l... Storage device, 2... Storage, 3... Modified air generation unit, 4... Air supply unit, 5... Gas concentration detection unit, 6... Programmable control, 7... 0! Sensor, 8...C02 sensor, 1
3... Three-way solenoid valve, 14... Air supply valve, 17.
...Compressor, 18...Dryer, 21...First adsorption tank, 22...Second adsorption tank, 43...Takeout valve, 44...0! Sensor, 45.46...0. Concentration meter, 47... CO concentration meter, 48... Start switch, 49... O7 concentration setting switch, 50...
C02 concentration setting switch.

Claims (1)

[Scope of Claims] A storage in which oxygen and carbon dioxide are maintained at a predetermined concentration ratio in order to maintain the freshness of stored items; an oxygen concentration detection means for detecting the oxygen concentration in the storage; and carbon dioxide in the storage. a carbon dioxide concentration detection means for detecting the concentration; an air supply means for supplying air to the storage; a modified air generation unit that generates air with a low oxygen concentration as modified air; and the oxygen concentration detection means and the carbon dioxide concentration detection means. Based on the detection signal from the means, the air supply means and the modified air generation unit are operated to supply atmospheric air or the modified air into the storage so that the oxygen concentration and carbon dioxide concentration in the storage are maintained at predetermined set values. A storage device comprising: a concentration control means for supplying water;