JPS6055110B2 - Equipment for storing perishable products in a gaseous medium with controlled low oxygen capacity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to refrigeration equipment and equipment, and in particular to storage of fresh fruits, vegetables, grapes, flowers, meat, fish, etc. in a gas medium with a controlled low oxygen capacity. ; Relating to equipment for storing perishable products.

Facilities for storage of products in gaseous media with low oxygen capacity are known (see: French Patent No. 1590579, Cl.A
23B5/00, 197@), which consists of a cooling chamber filled with a gas mixture, a gas exchanger with a selective membrane that communicates with the cooling chamber via a vibrine, and a circulating blower for the gas mixture. .

The gas exchanger includes a set of silicone polymer film sleeves connected through manifolds. The blower causes the gas mixture from the cooling chamber to pass through the sleeve and recirculate to the cooling chamber. Atmospheric air is blown through the sleeve. As a result of the difference in partial pressure, carbon dioxide (CO2), nitrogen (N2) and oxygen (
02) diffuses through the film.

That is, carbon dioxide and nitrogen generated by fruit respiration diffuse from the cooling chamber into the atmosphere, while oxygen from the atmosphere diffuses into the cooling chamber. Here oxygen is consumed by the fruit's respiration. However, when implementing this gas exchanger, the attainment of the intended composition of the gas medium in the cooling chamber is due to the oxygen concentration precisely due to the absorption of oxygen in the cooling chamber (by the process of fruit respiration). Because it decreases, it becomes very loose.

The absorption process proceeds very slowly because the oxygen concentration changes by no more than 0.5% per day, and the decrease in the amount of oxygen in the cooling chamber ultimately reduces the storage efficiency of the fruit. This is because the rate of decrease in oxygen capacity decreases over time. The gas exchanger produces a gas medium of a predetermined composition, since the medium is produced via oxygen absorption by the fruit in the cooling chamber and the gas exchanger through the membrane, in this installation there are no restrictions on the tightness of the cooling chamber. Very demanding.

Furthermore, when implementing the gas exchanger described above, it is not possible to control the gas medium composition within the cooling chamber.

This primarily relates to the fact that the gas medium composition in the cooling chamber is determined by the outflow velocity values and proportions of the mixture components through the membrane. These factors depend on the one hand on the diffusion properties of the membrane and on the other hand on the difference in partial pressure above and below the membrane. Since the air above the membrane is always below atmospheric pressure, the force of oxygen moving through the membrane from the atmosphere into the cooling chamber is always high. In this case, an equilibrium composition of the medium is formed in the cooling chamber, which depends only on the diffusion properties of the membrane. This makes it necessary to replace the membrane to change the gas medium composition. Other installations for storing perishable products are also known (see: JOuma
l66KhOlOdilnayaTekhnika''(
RefrigerationOn Engineering
), NO. elSp. 7, 198@), which consists of a closed cooling chamber and a gas separation device with a membrane separating two cavities and communicating with the atmosphere. The above-membrane cavity of the gas separator is connected to the cooling chamber through a blower that ensures circulation of the gas medium, while the under-membrane cavity of the gas separator is connected to a vacuum pump. This equipment allows the formation of a specific reduced pressure under the membrane;
Through selection of the required flow rate of the atmosphere in the submembrane cavity of the device, it is possible to vary the gas medium composition within the cooling chamber within a wide range. However, the efficiency of operation of the gas separation device in this installation is extremely poor if the required airtightness of the cooling chamber is not guaranteed. This is mainly related to the fact that if the cooling chamber is not sufficiently airtight, oxygen will penetrate into it. The rate of decrease in the gauge pressure of the gas mixture within the cooling chamber can serve as a measure of the airtightness of the cooling chamber. For example, is the gauge pressure in the cooling chamber 15? (water column) to 7.5w! t (water column) within 5 minutes, the oxygen concentration in the cooling chamber will have increased to 6-7% instead of the required 3%.
Furthermore, it is virtually impossible to maintain oxygen concentrations below 3% even in airtight cooling chambers, and large area membranes are required to operate the equipment satisfactorily under these conditions. A gas separation device with a This is because the larger the surface area of the membrane, the more nitrogen with high concentration will be produced, thus reducing the oxygen capacity in the gaseous medium. The invention aims at providing an installation for storing perishable products in a gaseous medium with a separated atmosphere and a low oxygen capacity, according to the invention:
It is possible to have a wide range of planned oxygen and carbon dioxide concentrations, and it is possible to quickly generate a gas medium with a planned composition under conditions that do not require strict airtightness of the cooling chamber. It gives you the opportunity to take control. To achieve this purpose, a membrane gas separation device having a cooling chamber, a submembrane cavity connected to a vacuum pump and an above membrane cavity connected to the cooling chamber and open to the atmosphere, and means for forced circulation of the gas medium are provided. An installation for storing perishable products in a gas medium controlled to a low oxygen capacity consisting of, on the one hand, a membrane cavity of a gas separation main device and, on the other hand, an outlet vibrator, according to the invention; at least one sub-membrane gas separation device similar to the main device having an above-membrane cavity communicating with the atmosphere through a sub-membrane cavity, the sub-membrane cavity of the sub-device being connected to a vacuum pump;
Therefore, the main gas separation device is connected to the atmosphere through the membrane cavity of the sub-gas separation device.

Through the use of gas separation subsystems, the required concentration of gas mixture can be produced fairly quickly.

This is because the atmosphere is made twice as concentrated as required in passing into the cooling chamber. In this way, the gas mixture passing from the gas separation subunit and already containing a low oxygen concentration is further enriched in nitrogen concentration in the main gas separation unit. For this purpose, the gas mixture introduced into the cooling chamber has a high nitrogen concentration and thus quickly reduces the oxygen concentration in the cooling chamber to 3%, even if tightness is not very strictly required, and this concentration can be maintained.
Furthermore, the gas mixture exhausted from the cavity of the gas separation main unit is immediately replenished by the concentrated nitrogen drawn in from the gas separation subunit. The presence of a reduced pressure in the cooling chamber and the inhalation of atmospheric air through non-tight wall joints can thus be avoided. In order to save costs and simplify the design of the equipment for the maintenance of a predetermined concentration of the gas medium, the cavity on the membrane of the gas separation sub-device is connected to the membrane of the gas separation device through means of forced circulation of the gas medium. Preferably, it is in communication with the upper cavity.

Additionally, the membrane cavity of the gas separation subsystem can be connected to the cooling chamber by a vibrator equipped with a valve.

In the installation of the invention, the outlet vibrator connecting the membrane cavity of the gas separation subsystem to the atmosphere can be connected to the cooling chamber via a vibrator equipped with a valve, whereby:
After placing the fruit in the cooling chamber, it is possible to quickly reduce the oxygen concentration in the cooling chamber due to the circulation of the gas mixture through the membrane cavity of the two-unit gas separator.

The equipment of the invention will become more clearly apparent in the detailed description of the invention with reference to the accompanying drawings, in which: FIG.

The installation according to the invention for storing perishable products in a gas medium with a controlled low oxygen capacity consists of an airtight or closed cooling chamber 1 (FIGS. 1 to 3), a membrane gas separation main It consists of a device 2 and sub-devices 3, a vacuum pump 4 and forced circulation means 5 for the gaseous medium, the controlled circulation means being of the conventional blower type.

Perishable products are placed in a cooling chamber filled with a gaseous medium with a low oxygen capacity. The main gas separation device 2 and the secondary device 3 are of the same type, each device being constructed as a system by a set of membrane elements contained in a housing, each device having a It consists of two cavities, of which the above-membrane cavity has a gas medium circulating at atmospheric pressure, and the under-membrane cavity is depressurized by a pump, and such main device 2 and sub-device 3 are installed in series with each other. ing. Depending on the volume of the cooling chamber 1, several membrane gas separation subsystems can be used in the installation according to the invention.
The membrane gas separation main and sub-devices consist of a set of selective membranes with different penetration rates for carbon dioxide, oxygen and nitrogen, and the gas separation devices 2 and 3 are separated into a plurality of cavities, i.e. the main The device 2 is partitioned into an upper membrane cavity 6 and a lower membrane cavity 7, and an upper membrane cavity 8 and a lower membrane cavity 9 in the sub-device 3. A gas separator is used.

The membrane cavity 8 of the sub-device 3 is connected on the one hand to the outlet vibrator 1
0 to the atmosphere, and on the other hand via a vibrator 11 to the membrane cavity 6 of the main gas separation device.

For this purpose, gas separation is required. The device 2 communicates with the atmosphere through the membrane cavity 8 of the membrane gas separation subdevice 3. The membrane cavity 6 of the main membrane gas separation device 2 (FIG. 1) is connected to the cooling chamber 1 by two vibrators 12 and 13. These vibrators 12 and 13 are equipped with means 5 for forced circulation of the girth medium. Submembrane cavities 7 and 9 of the gas separation device
(FIGS. 1-3) communicate with vacuum pump 4 through lines 14, 15 and 16.

Lines 14 and 15 are equipped with valves 17 and 18, which make it possible, when necessary, to close lines 14 and 15 and isolate one of the submembrane cavities from the vacuum pump. The submembrane cavity 7 of the main device 2 can be provided with a valve 19 with a valve 20 and can be intended to communicate this cavity 7 with the atmosphere when necessary.

In the equipment for storing perishable products shown in Figure 2, unlike the equipment shown in Figure 1,
The membrane cavity 8 of the submembrane gas separation device 3 communicates with the membrane cavity of the main membrane gas separation device 2 through means 5 for forced circulation of the gas medium.

The membrane cavity 8 of the gas separation subsystem 3 is connected to the cooling chamber 1 through a vibrator 21 having a valve 22 . on the other hand,
The membrane cavity 6 of the main gas separation device 2 communicates with the cooling chamber 1 through a vibrator 23 equipped with a valve 24 . This makes it possible to insulate the membrane cavity 6 of the device 2 from the cooling chamber 1 when necessary. In the equipment for storing perishable products shown in Figure 3,
Unlike the equipment shown in FIG.
A vibrator 10, which communicates the membrane cavity 8 of the ?

For this reason, the gas mixture in the cooling chamber 1 is
and 3, or only through the main device which provides nitrogen gas enriched by device 3. Cooling room 1 (Figures 1 to 3)
Inside is a sensor 27 inserted into the system that monitors the automatic adjustment of the gas mixture flow and controls the operation of all valves.
(gas analyzer or time relay) is installed. The sensor 27 and system for monitoring automatic adjustment of gas flow include:
Equipment well known to those skilled in the art is used. The equipment shown in Figure 1 of the accompanying drawings operates as follows.

When the vacuum pump 4 and the blower 5 are switched on, the gas medium begins to circulate counterclockwise between the cooling chamber 1 and the membrane gas separation device, and the membrane pressure drops to 01 absolute atmospheres. This fact results in a reduction in the partial pressure of carbon dioxide, oxygen and nitrogen across the membrane (in the submembrane cavity) and a diffusive flow of these components of the gas mixture through the membrane.
A portion of the gas mixture drawn from the cooling chamber 1 and then diffused through the membrane is passed into a concentrated nitrogen stream from the membrane cavity 8 of the secondary device 3 to the membrane cavity 6 of the main device 2 and further into the cooling chamber. It is then replenished. For this purpose, cooling chamber 1
The generation of reduced pressure within the cooling chamber 1 and the ingress of air/oxygen into the cooling chamber 1 through non-hermetic closures are no longer possible.

The high concentration of nitrogen is obtained during separation of the air supplied through the vibrator 10 over the membrane in the subsystem 3 in a conventional manner.

When passed through device 2, the concentrated nitrogen stream becomes even more concentrated with nitrogen in the membrane cavity of device 2. By that,
A low concentration of oxygen within the cooling chamber is ensured even if the joints of the cooling chamber walls are non-hermetic. From the secondary device 3 to the main device 2 there always passes an amount of gas equal to the amount of gas mixture that is evacuated through the membrane of the main device. Thereby, the existence of reduced pressure in the cooling chamber 1 is avoided. When the oxygen concentration in the cooling chamber 1 drops below the set value, the sensor 27 activates the valve 2.
0, the valve is slightly opened and a flow of atmospheric air is introduced into the submembrane cavity of the main device 2.

Oxygen enters through the membrane into the membrane space 6 of the device 2 and further into the cooling chamber 1. In this way, the oxygen concentration within the cooling chamber 1 increases. When the oxygen concentration in the cooling chamber 1 rises above the set value, the sensor 27 sends a signal to the valve 20,
Published on 17th and 18th.

Valve 20 is closed, blocking the flow of atmospheric air from the submembrane space 7 of the main device. In valves 17 and 18, on the other hand, the passage cross section increases, creating a reduced pressure in the submembrane cavity of both devices. In this way, the oxygen concentration in the cooling chamber is reduced by the diffusive exhaust through the membranes of devices 2 and 3.
To explain this more clearly, the reduction in partial pressure that occurs across the membranes of the primary and secondary devices causes gas to be transported across the membranes. A pressure builds up above the membrane, which is higher than the pressure below the membrane. The greater the pressure drop, the greater the rate of gas diffusion across the membrane.
The membrane may be a silicon/organic polymer structure based on polyvinyltrimethylsilane.

Under equal conditions, the penetration rates across the membrane of carbon dioxide, oxygen and nitrogen are 12:3:1, respectively. The penetration rate of carbon dioxide and oxygen is 12 and 3 times higher than that of nitrogen, respectively, and the membrane can be said to be selective for carbon dioxide and oxygen. If air at atmospheric pressure is supplied above the membrane, while reducing the pressure under the membrane, i.e. in the very manner in which this equipment works, air enriched with oxygen penetrates the membrane, while the selection of oxygen Air enriched with nitrogen due to natural diffusion accumulates on top of the membrane. At the same time, carbon dioxide is pumped out through the membrane and the carbon dioxide concentration decreases above the membrane. The larger the surface area of the membrane and the longer the distance gas travels over the membrane,
The nitrogen content in the gas mixture increases. A portion of the gas mixture escapes from the cooling chamber through the membrane of the main device during operation.

However, this condition does not reduce the pressure in the cooling chamber. The leakage flow is supplemented by a concentrated nitrogen flow through the membrane of the sub-equipment cavity, ensuring stable operation of the equipment even if the walls of the cooling chamber lose their air-tight efficiency. The installation shown in FIG. 2 is operated in much the same way as the installation of FIG. It is at this point that it is introduced into the main device 2 after being mixed with the gaseous medium supplied from the source. This further reduces the possibility of the creation of a reduced pressure in the cooling chamber 1 and the possibility of atmospheric air entering the cooling chamber through non-tight joints of the cooling chamber walls. The equipment shown in FIG. 3 is operated in essentially the same way as the equipment shown in FIG. 2, except that it is connected to the membrane space of the sub-unit 3. Vibrator 2 comprising a valve 26
5, the gas mixture can be circulated through the coupling devices 2 and 3, and the fruit can be directly placed in the cooling chamber. The latter is more effective. This makes it possible to quickly reduce the oxygen concentration in the cooling chamber from 20.7% to 10%. When an oxygen concentration of 10% is reached, the valve 26 is closed and the equipment is placed under the conditions described above, i.e. the gas mixture is circulated through the main unit 2, while high concentration nitrogen is introduced into the system through the secondary unit 3. It is operated by

Therefore, in the cooling chamber of the installation according to the invention, the formation and control of the gas medium composition is ensured under the condition of moderate requirements for the airtightness of the cooling chamber 1.

For example, in the cooling room, the gauge pressure is 15T1n (water column) to 7.5? (water column) change (i.e. 7.5 m!
(change in water column) occurs in 5 minutes. This makes it possible to reduce losses of perishable products due to microbiological and physiological pathogens by up to a factor of 1 compared to prior art installations.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an installation for storing perishable materials in a gas medium with a controlled low oxygen capacity.

Claims (1)

[Claims] 1. A membrane gas separation device 2 having a cooling chamber 1, a sub-membrane cavity 7 connected to a vacuum pump 4, and an above-membrane cavity 6 connected to the cooling chamber 1 and communicating with the atmosphere, and a gas Equipment for storing perishable products in a gaseous medium controlled to a low oxygen capacity, consisting of means for forced circulation of the medium, leading on the one hand to the membrane cavity 6 of the main gas separation device 2 and on the other hand, pipes at least one sub-membrane gas separation device 3 similar to the main device 2 with an above-membrane cavity 8 communicating with the atmosphere via 10 and an under-membrane cavity 9 of the sub-device;
is connected to a vacuum pump 4, and the main gas separation device 2 communicates with the atmosphere via the membrane cavity 8 of the sub-gas separation device 3. 2. The membrane cavity 8 of the gas separation sub-device 3 is connected to the membrane cavity 6 of the gas separation main device 2 through forced circulation means 5 of the gas medium and to the cooling chamber 1 through a pipe 21 with a valve 22. Equipment according to claim 1, characterized in that: 3. The pipe 10 connecting the membrane cavity 8 of the gas separation subsystem 3 to the atmosphere is connected to the cooling chamber 1 through a line 25 provided with a valve 26. Equipment described in any of paragraph 2.