EP0435893B1 - Installation for transporting and/or storing products affected by changes in temperature and humidity - Google Patents

Abstract

PCT No. PCT/FR89/00448 Sec. 371 Date Mar. 22, 1991 Sec. 102(e) Date Mar. 22, 1991 PCT Filed Sep. 7, 1989 PCT Pub. No. WO90/03321 PCT Pub. Date Apr. 5, 1990.The present invention relates to an installation for transporting and/or storing products sensitive to changes in temperature and humidity such as foodstuffs and in particular cocoa. The installation comprises a heat-insulated inner enclosure 1 containing such products and having upper and lower parts provided with openings 2, 3 to allow a surrounding gas such as air or a neutral gas to circulate through the inner enclosure. An outer enclosure surrounds the inner enclosure and is heat-insulated except for a portion of a its lower side walls. Means is provided for treating the circulating gas to reduce its relative humidity entering the inner enclosure to a value less than that of the gas-product equilibrium.

Description

The subject of the invention is a new installation for the transport and / or storage of products sensitive to variations in temperature and humidity.

Thus, the present invention has two main fields of application: storage and transport.

More specifically, the invention allows the realization of various storage facilities, such as silos, stores, warehouses, etc. and transport such as large containers, non-standard containers, pallet boxes, bags, cartons, packaging boxes, etc.

The products capable of being stored and / or transported, within the framework of the invention, are on the one hand powdered or granulated products, such as in particular food products such as cocoa, and on the other hand any object or material sensitive to humidity and requiring limited humidity.

In the particular field of transport, the invention allows the transport of a very wide range of goods between two countries with very different local temperatures.

Until now, the transport of tropical agricultural products from producing countries with hot and humid climates to consuming countries with temperate or cold climates is inevitably accompanied by physical phenomena of desorption, adsorption and condensation, i.e. moisture transfer inside the relatively closed volume that constitutes for example a container or a pallet box.

These physical phenomena are the cause of serious degradation of the products transported.

An installation according to the preamble of claim 1 is known from document FR-A-2 163 344. This installation comprises two refrigeration units and a fan for reaching and maintaining the load located inside the container at a constant temperature in an interval extremely reduced.

Some systems installed in specialized containers, such as natural ventilation, double partition, double floor, false ceiling, absorbent, etc. were able to limit, slow down or delay desorption phenomena, but none gave full satisfaction and made it possible to avoid the deterioration in quality noted on arrival, especially in the case of cocoa.

The present invention aims to solve the aforementioned drawbacks, by proposing an installation for the transport and / or storage of products sensitive to temperature and humidity variations, of a new design, which makes it possible to avoid any deterioration of the products even when these undergo significant variations in temperature and / or humidity over time.

• 1°- Réguler les transferts thermiques de l'ensemble contenu-contenant, de façon à ce que la température du contenu reste toujours supérieure à la température humide de l'air (ou d'un gaz neutre) en mouvement ;
• 2°- Utiliser les mouvements de convection de l'air (ou d'un gaz neutre) pour transporter les calories et l'humidité de la masse du contenu vers un point choisi du contenant ;
• 3°- Réchauffer et assécher l'air (ou un gaz neutre) saturé avant qu'il ne rentre en contact avec le produit, au moyen d'un échangeur thermique.

The invention is based on the application of the following three principles:

• 1 ° - Regulate the heat transfers of the whole contents-container, so that the temperature of the contents always remains higher than the humid temperature of the air (or of a neutral gas) in movement;
• 2 ° - Use the convection movements of the air (or of a neutral gas) to transport the calories and the humidity of the mass of the contents towards a chosen point of the container;
• 3 ° - Heat and dry the saturated air (or neutral gas) before it comes into contact with the product, using a heat exchanger.

More specifically, the solution according to the invention, to solve the technical problem posed, consists of an installation according to claim 1.

Thus, the present invention makes it possible for the first time to control and order the physical phenomena of air / product balance, while avoiding the loss of quality of the product stored or transported.

According to a particular embodiment of the invention, these processing means comprise a heat exchanger.

According to another characteristic of the invention, the aforementioned heat exchanger is arranged on the path of circulation of air or neutral gas, in the vicinity of the products, preferably in the lower part of said internal enclosure.

• d'une part, à sa partie supérieure dans ladite enceinte interne, et
• d'autre part, par exemple par l'intermédiaire de canaux, dans le volume compris entre lesdites enceintes intérieure et extérieure.

According to an advantageous embodiment of the invention, the aforementioned heat exchanger comprises an open cavity, preferably produced inside the thermally insulating wall forming the bottom of the aforementioned internal enclosure, and opening out:

• on the one hand, at its upper part in said internal enclosure, and
• on the other hand, for example through channels, in the volume between said interior and exterior enclosures.

Advantageously, this cavity is arranged substantially vertical to the upper opening of the internal enclosure, so as to create a chimney for the circulation of air or neutral gas.

According to a particular characteristic of the invention, the aforementioned heat exchanger further comprises a removable partition for separation with the products contained in the internal enclosure, produced for example in the form of a grid possibly connected to a plate disposed at the bottom of said internal enclosure.

According to another advantageous characteristic of the invention, one can provide in said cavity and / or in the condensate recovery zone, absorbent, adsorbent and / or reinforcing thermal mass of the exchanger or from the condensate recovery zone, for example iron wool.

Advantageously, this grid and this plate are made of a thermally conductive material, thus providing a thermal bridge between the internal volume of the aforementioned cavity and the internal enclosure.

• La figure 1 est une vue de principe en coupe frontale d'une installation conforme à la présente invention ; et
• La figure 2 en est une vue partielle en perspective avec arrachement, illustrant la partie formant échangeur thermique de cette installation.

The invention will be better understood and other aims, characteristics and advantages thereof will appear more clearly on reading the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of nonlimiting examples illustrating a currently preferred embodiment of the invention and in which:

• Figure 1 is a principle view in front section of an installation according to the present invention; and
• Figure 2 is a partial perspective view with cutaway, illustrating the part forming the heat exchanger of this installation.

For the sake of clarity of the demonstration, we have chosen to describe the invention in the particular context of its application to the transport of tropical agricultural products from products produced in hot and humid climates to consuming countries in cold climates.

Of course, this is only a particular example of implementation of the invention intended to better understand the different physical phenomena involved.

Taking the example of a product such as cocoa beans, the air-product equilibrium conditions at the start and at the end make it possible to understand the moisture transfers that occur inside a container. and their effect on the quality of the product transported.

When the container is closed in the producing country, the water content and the temperature of the product are generally homogeneous and the ambient air quickly equilibrates with the product without significant variation in its water content, even if this air has a temperature and hygrometry different from the equilibrium conditions.

Alternating humidity transfers, for example following a daily cycle comprising a night minimum and a day maximum respectively lower and higher than the humid temperature of the internal air (dew point), are tolerable and do not cause loss product quality.

On the other hand, during maritime transport, the outside temperature gradually decreases until it becomes permanently lower than the humid temperature of the internal air.

The air-product balance is thus broken and there is a great heterogeneity of the temperatures and the water contents of the product inside its mass. In the case of cocoa, at the same time mold develops and possibly overheating in certain places.

Such phenomena occur in any totally or partially enclosed volume and can be observed in all types of containers currently existing. In the particular case of insulated containers, it is at the opening of the doors on arrival that these phenomena inevitably occur.

Referring to Figures 1 and 2, we will now describe the specific arrangements of an installation according to the invention.

This installation comprises an internal enclosure 1 intended to contain the products to be transported and / or stored. The shape and dimensions of this enclosure 1 can be any and will be chosen according to the shapes and dimensions of the products to be transported and / or stored.

The internal enclosure 1 is thermally insulated, for example by means of insulating panels known per se, and comprises at least one opening in its upper and lower parts, allowing the circulation of air (or possibly neutral gas) through the Pregnant 1.

In the example shown, the enclosure 1 has an upper central opening 2 and a plurality of lower lateral openings 3 which will be described later.

This installation also includes an external enclosure 5 surrounding said internal enclosure 1 which, in the example shown has a generally parallelepiped shape. The external enclosure 5 is thermally insulated with the exception of at least one part, for example the lower part "a" of its side walls.

Thus, the internal wall of the enclosure 5 is thermally insulated along its upper horizontal wall 6 as well as along the upper part 7 of its four vertical side walls.

The thermal insulation of the bottom wall 8 of the enclosure 5 is ensured by the panel insulating the bottom of the internal enclosure 1 which rests on the bottom 8 of the external enclosure 5.

The installation according to the invention finally comprises a heat exchanger which will be disposed on the path of circulation of the air or of the moving neutral gas, in the vicinity of the products, for example in the lower part of the internal enclosure 1.

In the currently preferred embodiment, this heat exchanger comprises an open cavity 9 opening on the one hand to its upper part in the internal enclosure 1 and on the other hand, via channels joining the openings 3, in the volume between the indoor 1 and outdoor 5 speakers.

As shown in FIG. 2, the cavity 9 can be produced in the form of a channel, for example a parallelepiped, extending longitudinally in the middle part of the internal enclosure 1, and communicating via an assembly channels 12 extending parallel and transversely to said channel, with the space between the interior 1 and exterior 5 enclosures.

According to a preferred embodiment, the cavity 9 and the channels 12 will be produced in the panel insulating the bottom of the internal enclosure 1. The cavity 9 will preferably be arranged vertically, relative to the opening 2, so as to create a "chimney" in which the moving air will circulate.

This heat exchanger will further include a removable partition 10 for separation with the products contained in the internal enclosure 1. This partition will for example be produced in the form of a perforated plate forming a grid possibly connected to a plate 13 forming a floor on which the products to be transported and / or stored rest. The cavity-grid-floor assembly thus constitutes the heat exchanger.

Of course, other types of heat exchangers can be used in place of the one just described. In particular, it is possible to design an exchanger consisting of a tube crossing the floor and embedded in the mass of products to be transported and / or stored and the upper end of which would be in the form of an inverted U or any other type of exchanger.

Advantageously, there will be at each end of the channels 12 grids 14, 15, the shape of the fins (shown schematically in Figure 1) will reduce any drops of condensation to the outside of the cavity 9 at the orifice opening into said cavity and outwards at the level of the orifice opening into the space between the internal 1 and external 5 enclosures.

Thanks to the presence of the removable grid 10, the cavity 9 is accessible from its upper part and it is possible, for example, to introduce therein absorbent and / or adsorbent products and / or of a nature to increase the thermal mass of the exchanger.

The operation of the installation which has just been described is as follows. When products are introduced into the internal enclosure 1, for example at the embarkation port where the temperature is relatively high (for example 28 ° C.), the container-content assembly is in thermal equilibrium.

When the outside temperature decreases, the non-insulated part of the side walls cools the descending air and starts moving in the direction indicated by the arrows.

When the outside temperature is below the dew point of the internal air, this internal air while descending along the non-insulated part becomes saturated, releasing water by condensation on the cold wall of the external enclosure 5. The condensation water flows along this wall and is collected in a condensate recovery zone 16 located at the bottom of the enclosure 5, between the side walls facing the internal 1 and external speakers 5. The relatively cold air (for example 17 to 18 ° C) saturated enters the channels 12 through the openings 3 , then in the cavity 9 which then acts as a heat exchanger since it is in close proximity to the mass of the products, and therefore at the same relatively high temperature (27/28 ° C).

Taking into account the high specific heat of the products, the air entering the cavity 9 is heated (for example to a temperature of 23/24 ° C) and its relative humidity decreases to a value lower than the relative humidity of air-product balance (for example 65 to 70%).

Then, the air heats up on contact with the product (for example up to a temperature of 25 ° C) while being charged with humidity (tendency towards air-product equilibrium).

Arrived in the upper part of the natural chimney formed in the vertical plane of symmetry of the internal enclosure 1, the air reaches a temperature and a relative humidity substantially equal to that of the product (for example a temperature of 25 to 26 ° C and a relative humidity of about 75%).

The air having passed through the mass of products leaves through the upper opening 2 and moves in the free space situated between the internal and external enclosures; the natural convection movement shown in Figure 1 by arrows, being favored by the cooling of the air located near the cold wall.

As can be understood, a cycle takes place which gradually cools and dries the cocoa, without the condensation and molds generally observed in the containers used to date appear.

The homogeneity and progressiveness of the cooling and drying are obtained by the regulation of heat transfers and humidity transfers.

This convection regulation results from the heat and water exchange resulting from the specific conformation of the installation according to the invention.

To these transfers by convection are added transfers by conduction from the hottest zones to the coldest zones of the mass, naturally reinforcing the effects of homogeneity and progressiveness.

The advantages of the installation according to the invention are therefore numerous.

In particular, the invention allows the transport and / or storage of a wide range of products. These products can be transported both in bags and in bulk, which allows to take full advantage of the economic interest of the container.

The homogeneity and progressiveness of the cooling and drying guarantees the perfect preservation of the initial qualities and properties of the products.

• . une enceinte interne (1), thermiquement isolée, destinée à contenir lesdits produits et comportant en ses parties supérieure et inférieure au moins une ouverture (2, 3) permettant la circulation d'air ou de gaz neutre au travers de ladite enceinte ;
• . une enceinte externe (5), entourant ladite enceinte interne (1) et dont la paroi interne est thermiquement isolée, à l'exception d'au moins une partie de ses parois latérales, par exemple la partie basse, et en ce que l'on procède à un traitement de l'air ou du gaz neutre circulent au travers des produits, de manière à abaisser l'humidité relative de l'air ou du gaz neutre entrant dans ladite enceinte interne, de préférence jusqu'à une valeur inférieure à l'humidité relative d'équilibre air-produit.

It is understood that the invention also covers a method of storing products sensitive to variations in temperature and / or humidity, such as in particular food products such as cocoa, contained in devices in which said products are in a container. environment of neutral air or gas undergoing convection movements resulting in particular from temperature variations, characterized in that:

• . an internal enclosure (1), thermally insulated, intended to contain said products and comprising in its upper and lower parts at least one opening (2, 3) allowing the circulation of air or neutral gas through said enclosure;
• . an external enclosure (5), surrounding said internal enclosure (1) and the internal wall of which is thermally insulated, with the exception of at least part of its lateral walls, for example the lower part, and in that the the air or neutral gas circulating through the products is treated, so as to lower the relative humidity of the air or the neutral gas entering said internal enclosure, preferably to a value less than air-product equilibrium relative humidity.

As will be understood, the present invention is based on a static heat exchange between a product contained in a partially or completely enclosed volume and the ambient interstitial gas (possibly air).

One of the original features of the invention is not to use mechanical means to control the temperature and / or the hygrometric degree of a gas, but to use a static heat exchanger.

Claims (9)

1. Installation for transporting and/or storing products sensitive to changes in temperature and humidity, such as in particular foodstuffs such as cocoa, of the type comprising:

   - an inner enclosure (1) which contains said products, having in its upper and lower parts at least one opening (2,3) to allow air or a neutral gas to circulate through said inner enclosure (1);

   - an outer enclosure (5) surrounding said inner enclosure (1); and

   - means for treating the air or neutral gas circulating through the inner enclosure (1) in order to reduce the relative humidity of the air or neutral gas entering said inner enclosure,

   characterized in that said inner enclosure (1) is heat-insulated, in that said outer enclosure (5) is heat-insulated, with the exception of at least one part of its side walls, for example the lower part, and in that the air or neutral gas circulating through said inner enclosure undergoes movements of convection resulting in particular from variations in temperature at the level of the non-insulated part of the outer enclosure (5).
2. Installation according to claim 1, characterized in that said treatment means comprise a heat exchanger.
3. Installation according to claim 2, characterized in that said heat exchanger is disposed on the path of circulation of the air or neutral gas, in the vicinity of the products, preferably in the lower part of said inner enclosure.
4. Installation according to claim 2 or 3 and located in an environment of air or neutral gas undergoing movements of convection resulting in particular from changes in temperature, characterized in that said heat exchanger comprises an open cavity (9), preferably made inside the heat-insulated wall forming the bottom of said inner enclosure (1), and opening out, on the one hand, in its upper part in said inner enclosure (1), and, on the other hand, via channels (12), in the volume included between said inner (1) and outer (5) enclosures.
5. Installation according to claim 4, characterized in that said open cavity (9) is disposed substantially vertically with respect to the upper opening (2) of the inner enclosure, so as to create a shaft for the circulation of the air or of said neutral gas.
6. Installation according to claim 4 or 5, characterized in that said heat exchanger comprises a removable partition for separation from the products contained in the inner enclosure (1), made for example in the form of a perforated plate forming grate (10) possibly connected to a plate (13) disposed at the bottom of said inner enclosure (1), and forming floor.
7. Installation according to claim 6, characterized in that the grate (10) and the plate (13) are made of a heat-conducting material thus producing a thermal bridge between the inner volume of said cavity (9) and the inner enclosure (1).
8. Installation according to one of claims 4 to 7, characterized in that there may be provided in the cavity (9) and/or in the condensate recovery zone (16), materials which are absorbent, adsorbent and/or which reinforce the thermal mass of the exchanger or of the condensate recovery zone, for example steel wool.
9. Installation according to claim 1, characterized in that the means for treating said air or neutral gas are formed so as to reduce the relative humidity of the air or neutral gas entering the inner enclosure (1) to a value less than the air-product relative humidity.

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