EP0915748B1 - Method for impregnating hydrated fibrous organic matters, and installation for implementing the method - Google Patents

Description

Technical area

The invention relates to a method for impregnating materials. hydrated fibrous organic materials, such as, for example, wood, fruit, grains or oilseeds, skins. It relates to also facilities for the implementation of this process. More in particular, the invention relates to a method and installations permitting the impregnation of fibrous organic solids hydrated by self-evaporation of water of constitution under vacuum instantaneous and overpressure injection of a solute solution to be injected.

Previous techniques

In the following description and in the claims, by "hydrated fibrous organic materials" means any material fibrous organic comprising water of constitution occurring both in the form of free and residual water. As examples include wood, fruits, vegetables, grains of grains or oilseeds or skins, all of which have not undergone prior desiccation phase.

We know that organic fibrous matter loses instantly ten percent of their weight by spraying water from constitution without the volume of these matters being modified, when one heats these materials to 90 ° C, then when a vacuum is applied to them instantaneous at a very low pressure of the order of 0.07 bars.

• dans un premier temps, on élimine l'air disposé entre les multiples fibres du bois par dépression dans une enceinte hermétique.
• puis dans une seconde phase, on imprégne les plateaux de paraffine ou analogues.

In document FR-A-2 116 774, it has been proposed to treat wooden plans used in the form of trays or tables for food purposes in the following manner:

• firstly, the air disposed between the multiple fibers of the wood is removed by vacuum in an airtight enclosure.
• then in a second phase, the trays of paraffin or the like are impregnated.

Here the wood is pre-dried and has moisture residual in the range of seven to eight percent (7 to 8%) and therefore presents this fact, a pre-existing porous structure. In this process, the phase of vacuuming only causes deaeration intended to eliminate the air included in the wood fibers.

Document GB-A-15556 also describes a method of treatment of pre-dried wood, with almost total drying during operating phases and this by injection after degassing by vacuum effect.

• des durées de mise en oeuvre longues, de l'ordre de 5 minutes pour la mise sous vide, et de 10 minutes pour la mise en pression, ce qui ne provoquent pas de destructuration supplémentaire de la matière ;
• une pénétration en profondeur limitée, due à une destructuration insuffisante de la matière ;
• enfin, la mise en oeuvre d'un dispositif spécifique pour créer une forte pression de 5 à 10 bars pour l'injection.

These two processes use a material that has been previously dried and not wet, and essentially has the following drawbacks:

• long processing times, of the order of 5 minutes for the vacuum, and 10 minutes for the pressurization, which do not cause additional destructuring of the material;
• limited depth penetration, due to insufficient destructuring of the material;
• finally, the use of a specific device to create a high pressure of 5 to 10 bars for injection.

Furthermore, these processes are ineffective for other materials hydrated fibrous organics.

The invention relates to a method for impregnating at heart hydrated fibrous organic materials comprising water of constitution by means of a treatment liquid, such as for example a solution fungicide, a solution of hardening or flame retardant salts, a solution enzymatic for the treatment of wood, or a sugar solution for confectionery applications, or a salty solution for salted, or a solution of tannins for the treatment of the skins, etc ...

Brief description of the invention

• tout d'abord, à chauffer l'eau de constitution de la matière ;
• puis, à mettre en moins de 10 secondes ladite matière chaude sous une pression réduite, de manière à créer un réseau de micro-canaux assurant une communication sensiblement depuis le coeur jusqu'à la périphérie de la matière par effet de vaporisation d'une partie essentielle de l'eau de constitution ;
• puis, à mettre la matière ainsi traitée en contact avec un liquide d'imprégnation ;
• et enfin, à instaurer en moins de 1 seconde une surpression, de manière à faire pénétrer le liquide d'imprégnation dans les micro-canaux formés.

The invention relates to a method for impregnating a hydrated fibrous organic solid material comprising water of constitution, method comprising:

• first, to heat the water of constitution of the material;
• then, putting in less than 10 seconds said hot material under reduced pressure, so as to create a network of micro-channels ensuring communication substantially from the heart to the periphery of the material by the vaporization effect of a portion essential water of constitution;
• then, bringing the material thus treated into contact with an impregnating liquid;
• and finally, to set up an overpressure in less than 1 second, so as to make the impregnation liquid penetrate into the micro-channels formed.

• dans une première phase, à chauffer une matière organique fibreuse hydratée, c'est-à-dire contenant l'essentiel de son eau de constitution (eau libre et eau résiduelle), de préférence au voisinage de 100°C pour accumuler de l'énergie dans l'eau de constitution ;
• puis, dans une deuxième phase, à mettre rapidement ladite matière chaude sous une pression réduite en un temps très court, de l'ordre de quelques secondes, de manière à créer à l'intérieur de ladite matière un réseau de micro-canaux qui seront ainsi maintenus ouverts par la structure fibreuse et remplis uniquement de vapeur d'eau, lesdits micro-canaux se dirigeant essentiellement radialement depuis le coeur jusqu'à la périphérie de la matière grâce à l'effet de vaporisation d'une partie essentielle de l'eau de constitution libre ou résiduelle ;
• puis, dans une troisième phase, à mettre au voisinage de l'extrémité extérieure de ces micro-canaux une solution d'un liquide d'imprégnation qui, grâce à la condensation de la vapeur des micro-canaux, va créer un système d'aspiration de la solution placée en périphérie ;
• et enfin, dans une quatrième phase, à augmenter rapidement la pression, par exemple de l'ordre de la seconde, de manière à faire pénétrer à coeur le liquide d'imprégnation dans les micro-canaux formés.

In other words, the invention consists:

• in a first phase, to heat a hydrated fibrous organic material, that is to say containing most of its water of constitution (free water and residual water), preferably in the vicinity of 100 ° C. to accumulate energy in water of constitution;
• then, in a second phase, rapidly putting said hot material under reduced pressure in a very short time, of the order of a few seconds, so as to create inside said material a network of micro-channels which will be thus kept open by the fibrous structure and filled only with water vapor, said micro-channels running essentially radially from the heart to the periphery of the material thanks to the vaporization effect of an essential part of the free or residual water;
• then, in a third phase, to put in the vicinity of the outer end of these micro-channels a solution of an impregnating liquid which, thanks to the condensation of the vapor of the micro-channels, will create a system of aspiration of the solution placed at the periphery;
• and finally, in a fourth phase, rapidly increasing the pressure, for example of the order of a second, so as to make the impregnation liquid penetrate to the core in the micro-channels formed.

In the previous processes, the wood was always previously dried or brought to a low humidity level, so that it contains air in an existing porous structure as a result of drying. We therefore seeks to eliminate this air included by heating and then evacuating in order to fill the porous structure with a treatment product.

On the contrary, in the process according to the invention, the material is necessarily hydrated, that is to say with its water of constitution and is not therefore not porous and contains no air significantly.

The heating stage followed by the rapid evacuation stage by intermediate condensation of the emitted vapors, causes vaporization of the water of constitution and thus the creation of a structure porous which was not pre-existing. In this way, the micro-channels formed ensure perfect continuity of communication between the heart of the matter, that is to say the deepest zones and the periphery thereof. These micro-channels are only filled with steam. So, by internal condensation of this vapor, it is possible to impregnate the core of the material any treatment solution without having to use back pressure excessive.

The condensation of the water vapor is made instantly thanks to pressurization, the cold source then being constituted by the material itself.

The impregnation of fibrous substances with a dissolved substance in water or any other solvent, allows impregnation depth. This impregnation is done by means of a liquid previously heated to a temperature greater than or equal to the equilibrium temperature of the corresponding vacuum.

• le chauffage préalable de la matière (1ère phase) est effectué par tout moyen approprié, tel que par exemple la conduction avec une surface chaude ou avec un liquide chaud recirculant, voire par utilisation d'ondes haute-fréquence ;
• la mise sous vide instantanée (2ème phase) de la matière préchauffée provoque une auto-évaporation de l'eau de constitution qui crée dans cette matière un réseau nouveau de micro-canaux de vapeur différent de ce que l'on obtenait lors du séchage. L'importance du dégagement de vapeur d'eau instantané (voisin de 2,5 m³ émis en une seconde pour un kilo de matière traitée) fait que si les canaux existants sont utilisés pour l'évacuation de cette vapeur d'autres voies se créent, les premières étant insuffisantes pour assurer le débit ;
• la mise au contact avec le liquide d'imprégnation s'effectue à une température égale ou tout au plus légèrement supérieure à celle de la matière concernée, cette introduction pouvant se faire avant ou après la mise sous vide ;
• enfin, la mise sous pression très rapide de l'enceinte de traitement provoque l'introduction de la solution.

Advantageously, in practice:

• the prior heating of the material (1st phase) is carried out by any suitable means, such as for example conduction with a hot surface or with a hot recirculating liquid, or even by the use of high-frequency waves;
• the instantaneous vacuum (2nd phase) of the preheated material causes self-evaporation of the water of constitution which creates in this material a new network of micro-steam channels different from what was obtained during drying. The importance of the release of instantaneous water vapor (close to 2.5 m ³ emitted in one second for one kilo of treated material) means that if the existing channels are used for the evacuation of this vapor from other channels create, the first being insufficient to ensure the flow;
• the contact with the impregnating liquid is carried out at a temperature equal to or at most slightly higher than that of the material concerned, this introduction can be done before or after putting under vacuum;
• finally, the very rapid pressurization of the treatment chamber causes the introduction of the solution.

The proportion of micro-channels formed essentially depends on the difference between the reheating temperature and that corresponding to the vacuum. The greater this difference, the greater the volume of the micro-channels trained will be important.

In a preferred embodiment, the heating takes place at a pressure greater than 0.5 bar absolute, preferably at a pressure between 0.5 and 3 bars absolute, any of the known means in particular by conduction with a hot recirculating liquid or on a hot surface or steam condensation effect or use of high frequency heaters.

Reduced pressure takes place in less than ten seconds. Indeed, it has been found that for solids of minimum dimensions located between 5 and 15 cms, the optimal vacuuming time is less to ten seconds, preferably on the order of six seconds.

For solids with a minimum dimension between 2 and 5 cms, the ten seconds vacuuming times are satisfactory, the delay optimal being of the order of a second.

Finally, for solids whose minimum dimension is between 2 and 20 mm, the vacuuming time on the order of one second is satisfactory, the optimal duration being of the order of 0.1 to 0.2 seconds.

The contact of the impregnation liquid, previously heated at a temperature at least equal to the equilibrium temperature under vacuum, takes place without variation of the reduced pressure. So at the time of the introduction of the impregnation solution, the material undergoes no overpressure which would cause a slight entry of said solution into the matter, nor any condensation effect.

On the other hand, rapid pressurization takes place in a time of at least plus a second.

The invention also relates to two installations for setting up work of this process.

• des moyens de chauffage (E1,P1) de la matière à traiter contenue dans une chambre de traitement (CT) reliée :
  • d'un part, à une source de pression (SP) par une vanne (V3) ;
  • d'autre part, à une source de vide par une vanne (V1,V2), dont la rapidité d'ouverture permet de moduler le temps nécessaire à la mise en dépression de la chambre, la source de vide étant constituée d'un condenseur à mélange (CM) contenant une réserve d'eau froide (F) dans sa partie basse et comportant un circuit de recirculation de l'eau froide (E2,P2,P3), ce condenseur étant relié, en partie haute, par une tuyauterie, à un dispositif de vide (DV) ;
• des moyens d'introduction (DC) d'un liquide d'imprégnation dans la chambre de traitement (CT).

In a first embodiment, the subject of the invention is an installation for the discontinuous impregnation of a hydrated fibrous organic solid material, comprising water of constitution, installation comprising:

• heating means (E1, P1) of the material to be treated contained in a processing chamber (CT) connected:
  • on the one hand, to a pressure source (SP) by a valve (V3);
  • on the other hand, to a vacuum source by a valve (V1, V2), the speed of opening of which makes it possible to modulate the time necessary for the vacuuming of the chamber, the vacuum source consisting of a condenser mixture (CM) containing a cold water reserve (F) in its lower part and comprising a cold water recirculation circuit (E2, P2, P3), this condenser being connected, in the upper part, by a pipe , to a vacuum device (DV);
• means for introducing (DC) an impregnation liquid into the treatment chamber (CT).

• des moyens pour introduire en continu la matière à traiter dans une chambre de chauffe (CC) ;
• une chambre d'évaporation (EV) reliée, d'une part, à la chambre de chauffe (CC) par un sas (S1) permettant le passage de la matière à traiter et, d'autre part, à une source de vide (SV) ;
• une chambre d'imprégnation (CI,EG) reliée d'une part, à la chambre d'évaporation (EV) par un sas (S2) permettant le passage de la matière à traiter, et d'autre part, à un moyen (PC) de mise en surpression ;
• des moyens d'amenée d'un liquide d'imprégnation dans les chambres d'évaporation et d'imprégnation.

In a second embodiment, the subject of the invention is an installation for the continuous impregnation of a hydrated fibrous organic solid material comprising water of constitution, installation comprising:

• means for continuously introducing the material to be treated into a heating chamber (CC);
• an evaporation chamber (EV) connected, on the one hand, to the heating chamber (CC) by an airlock (S1) allowing the passage of the material to be treated and, on the other hand, to a vacuum source ( SV);
• an impregnation chamber (CI, EG) connected on the one hand, to the evaporation chamber (EV) by an airlock (S2) allowing the passage of the material to be treated, and on the other hand, to a means ( PC) overpressure;
• means for supplying an impregnation liquid into the evaporation and impregnation chambers.

Brief description of the figures

Figure 1 is a representation of an installation for setting discontinuous work of the process according to the invention.

Figures 2a to 2d are schematic representations of the process according to the invention by means of the installation of FIG. 1.

Figure 3 is a summary representation for the implementation continuous process according to the invention.

Ways to realize the invention

As already said, the implementation of the method according to the invention can be done discontinuously, i.e. by submitting the same quantity of materials to be treated successively at the different stages of the process, either continuously, i.e. by circulating the material in different enclosures ensuring each of the process functions.

Processing discontinuously (Figures 1 and 2)

The installation described diagrammatically in FIG. 1 makes it possible to treat discontinuously the different types of materials referred to in the preamble.

Thus, this installation mainly comprises a treatment (CT), a mixing condenser, a pressure source (SP), a vacuum device (DV), these different elements being interconnected by a network of pipes and valves, as well as appropriate recirculation. More specifically, as seen in Figure 1, the treatment chamber (CT) can consist of an enclosure, the autoclave type, for example stainless steel, pressure resistant and empty.

This enclosure is associated with means for heating the material to treat which can be of various natures. For example, like shown, it can be a recirculation and heating circuit liquid consisting of a pump (P1) and a surface exchanger (E1) whose function is to recover the liquid present in the bottom of the treatment chamber (CT) and reheat it then spray it on the material to be treated.

Obviously, other means can be used such as heating by high frequency waves (not shown), or advantageously by a device (DC) allowing the introduction of the pre-heated impregnation solution which thus serves as a vector calories.

This treatment chamber (CT) is connected to the pressure source (SP) via a quick opening valve (V3), i.e. less than one second.

This treatment chamber (CT) is also connected to the mixing capacitor (CM) by means of two valves (V1, V2) via tubing (T1, T2) of different section. In this way, depending on the circuit selected (T1, T2), and the opening speed of the valves (V1, V2), it is possible to adjust the vacuuming time.

The mixing condenser (CM) also consists of a steel enclosure, possibly stainless. So completely essential, it contains a reserve of cold water (F), i.e. temperature significantly lower than that of the steam extracted from the material to be treated, and typically of the order of at least 25 ° C. This mixing condenser (CM) is associated with a recirculation circuit of cold water consisting of an exchanger (E2), for example of the type exchanger by surface, then from one or two centrifugal pumps (P2, P3) to broadband.

This mixing condenser (CM) is connected to a vacuum device (DV) consisting essentially of a vacuum pump and so advantage of a vacuum level regulation system, in order to obtain optimal performance.

The implementation of the process thanks to this installation is carried out the following way.

In a first phase, illustrated in FIG. 2a, the material to be treated (M) is introduced into the treatment chamber (CT). It is heated there by any appropriate means already mentioned such as traffic and heating the impregnation solution which then constitutes the vector of calories, or else, more conventionally by introducing steam, or even by heating with high frequency waves

In this way, the water of constitution contained in the material to be treated is brought to a high temperature.

In the following, the valves (V1) and (V2) are open in order to set up communication the treatment chamber (CT) with the condenser mixture (CM) itself under very reduced pressure, of the order of 0.07 bar absolute at 0.09 bar absolute. It follows that this almost instantaneous vacuuming preheated material, causes self-evaporation of the water of constitution of the fibrous material (see Figure 2b). This evaporation creates in the material a network of micro-channels (5) of vapor connecting the heart of the material with its periphery.

The extracted steam enters the mixing condenser and is condensed thanks to the presence of sprayed cold water which serves as reserve of frigories.

In the subsequent step, illustrated in FIG. 2c, the contact is brought into contact. material to be treated (M) with the impregnation solution (1). Well obviously, in the case where the material to be treated has been heated thanks to the impregnation solution, there is no need to additional solution introduction.

The valves (V2) and (V1) are then closed, which maintains inside the treatment chamber (CT) reduced pressure, close from that generated by the vacuum device.

In the next phase, illustrated in Figure 2d, the valve (V3) is open and therefore the treatment chamber (CT) is put almost instantly overpressure. This causes the introduction of the solution in the micro-channel network, right down to the heart of the matter.

Continuous implementation (Figure 3)

The installation described in Figure 3 allows continuous processing of the material by passing it successively through various enclosures to inside which the different phases of the process are carried out according to the invention.

More specifically, this installation includes a heating (CC), an evaporation chamber (EV), a chamber impregnation (CI), an overpressure zone (EG), and a vacuum source (SV). These different elements are linked by systems circulation and appropriate airlock.

More specifically, the heating chamber (CC) is constituted by a enclosure open upwards to the water inside which are introduced the materials to be treated. As for the treatment chamber corresponding to the discontinuous process, this heating chamber (CC) can be equipped with different means of heating the material, namely a high frequency device (HF), or a water circulation circuit hot or hot impregnation solution consisting of a pump (PCH) drawing from the bottom of the heating chamber and bringing the hot water in a surface exchanger (ECH), then ensuring the ascent of the water hot to the top of the heating chamber (CC) for its spraying on the material to be treated.

In the lower part, the heating chamber includes a tubing (T5) equipped with a supply means, such as a screw Archimedes (6) followed by a positive displacement pump, which ensures the transport of the heated material to the evaporation chamber (EV).

Obviously, the invention covers alternative embodiments various in which the Archimedes screw can feed a rotary airlock or an airlock consisting of two guillotine valves.

The evaporation chamber (EV) consists of an enclosure of the autoclave type, vacuum resistant, for example stainless steel. This evaporation chamber (EV) is connected, in the upper part, to the vacuum source (SV). In the lower part, the evaporation chamber (EV) includes advantageously a scraper device (7) allowing, by means of various advantageously oriented rotary blades (8), to bring the material towards the axis of symmetry of the evaporation chamber (EV). The bottom of the evaporation chamber (EV) has an opening (10) connected to a airlock (S2) or to an equivalent pump not shown, which connects this evaporation chamber (EV) to a tank (CI) for contacting the material with the impregnation solution (1).

For information, the vacuum source (SV) is for example a assembly comprising a condenser, a vacuum pump or the like vacuum device, a condensate extraction pump.

Advantageously, this impregnation tank (C1) comprises a circuit for sampling the impregnation solution which leads to the by means of a pump (PS), said solution after heating to inside the evaporation chamber (EV), so as to ensure bringing the treated material into contact with the impregnation solution (1) at the time of spraying.

The impregnation tank (CI) is connected to the solution tank impregnation and includes a level regulator (LC) allowing control the progress of the process.

The impregnation tank (CI) inside which the material is immersed in the impregnation solution (1) is then in overpressure with respect to the evaporation chamber.

The impregnation tank (CI) is connected to a setting area overpressure constituted by a tube comprising a screw Archimedes (11) ensuring the elevation of the material for its outlet (12) from the installation.

More specifically, this Archimedes screw (11) is driven by a motor not shown at a speed calculated to ensure a time of stay under pressure sufficient to induce impregnation at the heart of matter.

The value of the overpressure to which the material to be treated is subjected is controlled by the pressure regulator (PC) connected to the screw Archimedes (11).

Finally, this Archimedes screw ends in the airlock (S3), or a equivalent pump, allowing the return of constant pressure.

• l'imprégnation en profondeur de bois avant séchage par des produits fongicides permettant d'améliorer la longévité d'utilisation ;
• l'imprégnation des graines de céréales par une solution enzymatique afin de liquéfier l'amidon en évitant par là une mouture préalable ;
• l'imprégnation de fruits fibreux tels que des pommes ou des ananas par une solution sucrée afin de réduire le temps de préparation lorsque l'on désire confire ces fruits ; éventuellement, le procédé peut être appliqué par imprégnations successives ;
• l'imprégnation de graines oléagineuses par des solutions facilitant l'extraction des matières grasses ;
• l'imprégnation de racines, tels que les betteraves sucrières pour les épurer à coeur ;
• l'imprégnation de peaux par des solutions de tannage.

The method and the installations according to the invention can be used with success for the impregnation of any hydrated fibrous or tissue substance capable of being impregnated with a solvent such as water or by any liquid capable of being volatilized by heating followed by depressurization, said liquid being able to dissolve the substance chosen in the impregnation. As an example, we can cite:

• the deep impregnation of wood before drying with fungicidal products to improve the longevity of use;
• impregnating the cereal seeds with an enzymatic solution in order to liquefy the starch, thereby avoiding prior grinding;
• the impregnation of fibrous fruits such as apples or pineapples with a sweet solution in order to reduce the preparation time when it is desired to preserve these fruits; optionally, the process can be applied by successive impregnations;
• the impregnation of oil seeds with solutions facilitating the extraction of fat;
• the impregnation of roots, such as sugar beets to purify them to the core;
• the impregnation of skins with tanning solutions.

Claims (9)

1. Method for impregnating a hydrated fibrous organic solid material comprising water of constitution, method consisting:

   first of all, in heating the water of constitution in the material;

   then in placing, in less than 10 seconds, the said hot material under a reduced pressure so as to create a network of microchannels providing substantial communication from the centre to the periphery of the material by the effect of vaporization of a major portion of the water of constitution;

   then, in placing the material thus treated in contact with an impregnation liquid;

   and finally, in establishing in less than 1 second an excess pressure so as to cause the impregnation liquid to penetrate into the microchannels formed.
2. Method according to Claim 1, characterized in that the heating of the water of constitution in the material is obtained by conduction with a hot surface.
3. Method according to Claim 1, characterized in that the heating of the water of constitution is performed by conduction with a circulating hot liquid.
4. Method according to Claim 1, characterized in that the heating of the water of constitution is performed by high-frequency waves.
5. Method according to Claim 1, characterized in that the heating of the material to be treated is performed at a pressure greater than 0.5 absolute bar and less than 3 absolute bar.
6. Method according to Claim 1, characterized in that the bringing of the material to be treated into contact with the impregnation liquid is performed at a temperature which is slightly greater than or equal to that of the material to be treated.
7. Method according to Claim 1, characterized in that the bringing of the material to be treated into contact with the impregnation liquid is performed without variation of the reduced pressure.
8. Plant for carrying out the method according to Claims 1 to 7, for the batch impregnation of a hydrated fibrous organic solid material comprising water of constitution, which plant comprises:

   means for heating (E1,P1) the material to be treated contained in a treatment chamber (CT) connected:

   on the one hand, to a source of pressure (SP) via a valve (V3);

   on the other hand, to a source of vacuum via a valve (V1,V2), whose speed of opening makes it possible to modulate the time necessary for the chamber to be placed under vacuum, the source of vacuum consisting of a mixture condenser (CM) containing a cold water reserve (F) in its lower portion and comprising a cold water recirculation circuit (E2,P2,P3), this condenser being connected, at the top part, by a system of tubes, to a vacuum device (DV);

   means for introducing (DC) an impregnation liquid into the treatment chamber (CT).
9. Plant for carrying out the method according to Claims 1 to 6, for the continuous impregnation of a hydrated fibrous organic solid material comprising water of constitution, the plant comprising:

   means for continuously introducing the material to be treated into a heating chamber (CC) ;

   an evaporation chamber (EV) connected, on the one hand, to the heating chamber (CC) via a lock chamber (S1) allowing the passage of the material to be treated and, on the other hand, to a source of vacuum (SV) ;

   an impregnation chamber (CI,EG) connected, on the one hand, to the evaporation chamber (EV) via a lock chamber (S2) allowing the passage of the material to be treated and, on the other hand, to a means (PC) for placing under excess pressure;

   means for conveying an impregnation liquid into the evaporation and impregnation chambers.

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