RU2118485C1 - Perishable product storage method - Google Patents

Abstract

FIELD: storage of agricultural products, in particular, providing controllable medium for prolonged storage of perishable products. SUBSTANCE: method involves placing products in chamber; dividing medium with products into hermetically sealed volumes; creating and maintaining controlled gaseous medium by communicating hermetically sealed volumes in predetermined sequence depending on kind of product to be stored; maintaining parameters of gaseous medium in each volume by generating return gas flows from gaseous medium of hermetically sealed volumes and ambient air or nitrogen and keeping individual temperature and gaseous medium composition at required level. EFFECT: reduced costs for keeping controlled gaseous medium parameters and improved quality of product. 2 cl, 3 dwg, 1 tbl

Description

 The invention relates to methods for creating controlled gas environments in airtight containers in which long-term storage of perishable products is carried out.

Known methods for long-term storage of perishable products that use controlled gas environments of various compositions. So, in the method of storage of grapes (SU 1738140 A1 publ. 07.06.92, Bull. N 21, MKI A 01 F 25/00, A 23 B 7/152) the grapes are pre-cooled and placed in a sealed container disinfected with sulfur dioxide, in which create a gas medium containing carbon dioxide 20-70%, oxygen 4-6%, nitrogen - the rest, and incubated in it for the first 1-7 days. Subsequent storage is carried out with free access to air and with monthly treatment with sulfur dioxide in an amount of 1.0-1.5 g / m ³ .

 Examples of specific performance of this method are presented in the table.

 The disadvantage of this method is the limited application and the complexity and complexity of processing stored products.

 The closest in technical essence and the achieved result to the proposed one is a method and a container for storing products (ЕВП (EP) N 0368678, publ. 16.05.90, N 20, MKI B 65 D 88/74, A 23 L 3/34), at which the levels of oxygen and carbon dioxide inside the container are maintained at a predetermined level. Normative target levels of oxygen and carbon dioxide are selected depending on the type of product being stored (these levels are generally well known and can be established using simple experiments).

 The oxygen level inside the container is controlled by directing the nitrogen-enriched gas inside the container. Nitrogen-rich gas is added in a small amount, but regularly, approximately 1% of oxygen. Nitrogen-enriched gas is obtained from ambient air outside the container through an air separator, which is located in an enclosed space, in front of the container. If the level of carbon dioxide is below the normal level, then carbon dioxide is directed inside the container to normal. Carbon dioxide is supplied from the dry ice storage located inside the container.

 A feature of the air separator is that the surrounding air is pumped under pressure through the cavities of semipermeable membranes consisting of microscopic hollow fibers. T. about. at the outlet of the air separator we have separately oxygen and nitrogen. Oxygen penetrates through the fiber walls, while nitrogen passes through the channel of the hollow fiber.

 In addition, the compressor can quickly interact with the carbon dioxide level controller, and if the level of carbon dioxide rises above the permissible maximum, then the nitrogen-enriched gas is sent to the container for diluting carbon dioxide to normal.

 Gases circulating inside the container using a fan may be subjected to heat treatment through the use of a refrigeration system.

 Due to leaks from the container and the respiratory capacity of the loaded product, the environment inside the container can change continuously. It is also continuously restored to normal with the appropriate actions of the air separator and control valve.

Thus, the main characteristic features of the method are that nitrogen-enriched gas is supplied from the air surrounding the container and carbon dioxide from the dry ice storage located inside the container;
nitrogen-enriched gas is obtained by using an air separator of this type, which consists of membranes that separate air from the environment surrounding the container under pressure into nitrogen and oxygen, respectively;
nitrogen-rich gas is directed inside the space of the aforementioned container, in case the level of carbon dioxide exceeds the maximum allowed by the norm.

The main disadvantages of the above method of creating a controlled gas environment (CGS) in a container:
maintaining a constant temperature and composition of the CWG in the entire volume of the container, filled with various types of perishable products;
the creation of a controlled gas environment only from the air when the gas stream moves from the source of the CWG to the cargo container in the presence of significant leaks in it leads, ultimately, to significant economic costs when creating storage devices for products and maintaining the specified concentrations of the CWG;
the difficulty of maintaining a given level of temperature and concentration of a controlled gas medium in a large container volume;
maintaining the concentration of CO ₂ with dry ice in a thermally insulated box reduces the useful volume of the cargo container;
the complexity of the devices and the complexity of the presented method of storing perishable products, which does not allow developing product storage devices for the mass consumer, in which the concentration levels are set and regulated using various RGS controllers.

 It is proposed to create a CWG of a certain temperature and concentration using reverse gas flows, after dividing the gas media with perishable products into small volumes of a standard type.

 To this end, in the method of storing perishable products, in which they are placed in a chamber and create an inside controlled gas environment from carbon dioxide and nitrogen-enriched gases, using ambient air to produce the latter, according to the invention it is proposed to previously divide gas media with products into small volumes of a standard type (containers ), and the parameters of the gaseous medium to support the formation of reverse gas flows from the gaseous medium of the container and the surrounding air and the recharge of the gaseous medium by Yemen interval characterizing the degree of leakage of the system storage.

 In this case, the movement of the gas medium can be set by switching the sequence of the connection of small volumes with the product. To individually maintain the temperature of the gas mixture inside each small volume (container), depending on the type of stored product, the composition of the gas medium is set by feedbacks and thermostatic control systems.

The main differences of the proposed method are as follows:
I. CWG are obtained from the CWG container and ambient air due to the formation of reverse gas flows;
II. RGS recharge is carried out over a time interval characterized by the degree of leakage of the product storage system;
III. to accurately maintain the parameters of the controlled gas environment (mainly due to eliminating gas leakage points) in the entire volume of stored products, the gas medium and products are enclosed in small volumes of the standard type;
IV. in each small volume of products support RGS at a given temperature and a specific composition. The composition of the CWG is set by feedbacks and thermostatic systems of the CWG, allowing for individual maintenance of the temperature of the CWG within each small volume, depending on the type of products stored there;
V. The movement of the CWG is set by switching the sequence of small volumes with the product.

 Examples of the proposed method are presented graphically in FIG. 1-3.

 In the presented example (Fig. 1), a variant of the perishable goods storage mode is implemented, in which pure nitrogen from the source "A" is pumped by the fan "B" through the filter "F" and then enters the containers Кн1 - Кн3. In order to overcome the large hydraulic resistance created by perishable products in containers, another fan “B” is installed after them, which facilitates the passage of the gas mixture through the product.

A characteristic feature is that the creation of the CWG is carried out by the supply of nitrogen (liquid or gaseous) from an external source, taking into account that the increase in the concentration of O ₂ will occur due to infiltration from the surrounding air, and the content of CO ₂ due to the biological respiration of the stored products. Possible overpressure of the gas mixture is vented through the PC safety valve.

 The containers have a fairly high degree of tightness and are interconnected in a certain sequence by quick-disconnect connectors with check valves into packages; check valves allow one or more containers to be removed from the common package with minimal loss of gas mixture.

 In FIG. Figure 2 shows the option when the air from the containers and the environment is sucked in by the compressor "K" and pumped through the filter "F" - a moisture-oil separator into a membrane gas separation apparatus (GRA). After it, the nitrogen-enriched mixture enters the heat treatment and nitrogen enrichment unit “TO”, from where the gas mixture with certain parameters (RGS1, RGS2, RGS3) is supplied to a specific group of packages from the containers “Kn1 ... Kn4”. In each group of container packages there may be various types of perishable products that require individual supply of CSGs with certain parameters.

Then the gas mixture under pressure passes through the containers and captures with it the water vapor and CO ₂ , which are the waste products of the stored plant products. The interconnected containers together with a gas separation apparatus and a compressor form a closed circulation circuit. Due to the fact that in the gas separation apparatus air is divided into oxygen-and nitrogen-enriched gas mixtures, and the gas circulation system is closed, the compressor suction pipe begins to pick up a larger amount of the gas mixture from the containers than enters them from the GRA. In order to compensate for the resulting vacuum, the suction pipe is equipped with a calibrated hole "KO" in communication with the atmosphere. To prevent atmospheric air from leaking into containers when the compressor stops, the pipeline is equipped with an OK check valve.

 The exhaust gas mixture is compressed by a compressor, cleaned in the filter with a water-oil separator, and then the cycle of separation of the gas mixture is repeated.

 Note that in this embodiment, the gas medium is enriched with nitrogen through the use of a membrane gas separation apparatus with subsequent circulation and regeneration of the nitrogen-air gas mixture.

In the embodiment of FIG. In option 3, the system works in the same way as in the second option. The difference is that the source of pure nitrogen "A" is connected to the heat treatment unit "TO" and enriches the nitrogen-air mixture with pure nitrogen. This allows you to more quickly achieve gas modes with a high nitrogen content (up to 97 - 98%). Thus, the creation of the CWG is carried out in a combined way - due to the membrane gas separation apparatus and nitrogen recharge from an external source. The following notation is accepted here:
A is a nitrogen tank
K - compressor
Kn1 ... Kn4 - container N 1 ... N 4, respectively,
T ₁ ... T ₃ - temperature RGS in various volumes with products
RGS1 ... RGS4 - various compositions of controlled gaseous media,
F - filter
B - fan
THEN - heat treatment unit,
PC - safety valve,
GRA - gas separation apparatus,
OK - check valve,
KO - calibrated hole.

 Thanks to the use of the above method, it becomes possible to reduce operating costs for the creation and maintenance of CWGs while simplifying the design and expanding the range of stored products by creating and maintaining optimal storage parameters acceptable for each type of perishable product.

Claims (2)

 1. A method of storing perishable products, including putting them into the chamber, creating an adjustable gas environment from nitrogen-enriched and carbon dioxide gases using ambient air, characterized in that the gas medium with the products in the chamber is previously divided into sealed volumes, and maintaining the parameters of the gas medium in each hermetic volume, they are connected in a certain sequence determined by the composition of the gaseous medium, forming in each hermetic volume and parameter which are recommended for storage of agricultural products in the next sealed volumes.  2. The method according to claim 1, characterized in that maintaining the parameters of the gaseous medium is carried out by forming reverse gas flows from the gaseous medium of sealed volumes and ambient air or ozone and individually maintaining the temperature and composition of the gaseous medium inside each of the volumes, depending on the type of stored product .

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