EP0617247A1 - Cryogenic liquid recycling device and its application in a product freezing apparatus - Google Patents

Cryogenic liquid recycling device and its application in a product freezing apparatus Download PDF

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Publication number
EP0617247A1
EP0617247A1 EP94400456A EP94400456A EP0617247A1 EP 0617247 A1 EP0617247 A1 EP 0617247A1 EP 94400456 A EP94400456 A EP 94400456A EP 94400456 A EP94400456 A EP 94400456A EP 0617247 A1 EP0617247 A1 EP 0617247A1
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EP
European Patent Office
Prior art keywords
tank
liquid
circuit
cryogenic liquid
cryogenic
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94400456A
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German (de)
French (fr)
Inventor
Jean-Pierre Germain
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Application filed by Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Publication of EP0617247A1 publication Critical patent/EP0617247A1/en
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D3/00—Devices using other cold materials; Devices using cold-storage bodies
    • F25D3/10—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air

Definitions

  • the present invention relates to a device for recycling a cryogenic liquid and, more particularly, to such a device designed to supply a circuit comprising at least one section substantially at ambient pressure, typically in the open air, such as they are found in an application of the invention to the freezing of food, pharmaceutical or veterinary products.
  • the present invention therefore aims to achieve, in a simple, flexible and efficient manner, a device for recycling a cryogenic liquid in a circuit, which is not dependent on pumps to ensure the circulation of the liquid in the circuit and which does not causes no pollution of this liquid.
  • the present invention also aims to provide such a device which is capable of supplying a circuit comprising a section substantially at atmospheric pressure such as a freezing tunnel of products or these are immersed in a stream of cryogenic liquid.
  • a recycling device of the above-mentioned type comprising a) a first cryogenic tank. to recover said liquid at the outlet of said section, this tank being provided with means for pressurizing the collected liquid, b) a second cryogenic tank constantly pressurized in operation and connected to the circuit upstream of said section to supply it with cryogenic liquid pressurized, this second tank being in selective fluid communication with the first tank, and c) means sensitive to a predetermined relationship of the filling levels of the two tanks to selectively activate the pressurization means of the first tank so as to transfer into the second reservoir of the cryogenic liquid contained in the first reservoir.
  • the latter can supply the circuit with recycled and repressurized liquid, which ensures the circulation of the liquid without pump, and therefore without pollution.
  • the present invention also relates to a simple and reliable apparatus for freezing products comprising at least one device as defined above.
  • the device of FIG. 1 is used to supply, with a cryogenic liquid such as liquid nitrogen, a circuit 1 passing through a tank 2 in which quenching bottles 31, 32, 33, etc. .. containing products to be frozen, food, pharmaceutical or veterinary for example.
  • the device essentially comprises first and second cryogenic liquid tanks 4 and 5 respectively, each comprising a conventional double-walled container 41, 42, and 51, 52, respectively.
  • Each container 4,5 is further provided with internal pressurization means comprising a coil 43, 53, respectively, conventionally installed between the bottom of the wall 41, 51 and the blocked neck of this same wall.
  • each coil 43, 53 there is in series, a pressure regulating valve 61, 62 and a solenoid valve 71, 7 respectivement, respectively.
  • the tanks 4,5 are also equipped with air release solenoid valves 81, 82, liquid level sensors 91, 92, pressure gauges 101, 102 and pressure switches 111, 112 respectively. All the solenoid valves are controlled by electronic means contained in a cabinet 12 which receives the signals supplied by the pressure switches and the level sensors 91, 92, the levels of the tanks 4.5 being able to be displayed on the cabinet in 131, 132, respectively.
  • the level sensors can be of the conventional type, with a rod, or of the type described in patent application EP-A-530,102.
  • the reservoir 4 collects, by a funnel 21 and a conduit 14 equipped with a solenoid valve 15 also controlled by the cabinet 12, the liquid nitrogen at atmospheric pressure which leaves the freezing tank 2.
  • the nitrogen thus recovered can, under conditions which will be described later, be returned to the tank 5, by a conduit 16 equipped with a solenoid valve 17 controlled by the electronic means contained in the cabinet 12.
  • the reservoir 5 is used to supply the circuit 1, through a valve 18 which can be manually controlled.
  • the reservoir is itself supplied, according to the present invention, either by an external source 20, through a solenoid valve 19, or by the reservoir 4, as explained below in the description of the operation of the device according to the invention.
  • the solenoid valves: 71, 17.82, 19, are normally closed 81, 15.72, are normally open
  • the pressure switch 111 emits a signal when the pressure in the tank 4 reaches a predetermined level authorizing a transfer of nitrogen under pressure to the tank 5.
  • the pressure switch 112 is used to continuously regulate the pressure in the tank 5, at another predetermined level. To do this, the pressure switch emits "high” and "low” signals representative of pressures framing this predetermined level.
  • the nitrogen distribution tank 5 is filled in the circuit 1.
  • the electronic control means energize the solenoid valves 19 and 82 (from normally open air) which therefore open, as does the normally open solenoid valve 72 which then closes.
  • the other reservoir 4 must at this time be inactive, and to do this, the solenoid valves 17, 15, 7 and 8 are kept de-energized.
  • the external source 20 of nitrogen under pressure is then emptied into the tank 5 through the open solenoid valve 19, until the level sensor 92 indicates to the electronic means contained in the cabinet 12 that the maximum filling level of the reservoir 5 is reached.
  • the reservoir 5 being filled, it is possible to put the device into service so that it delivers in the circuit 1 the liquid nitrogen which it contains.
  • the valve 18 is opened and the control means put or maintain the electrovalves 81, 71, 15,17 on the one hand and the electrovalves 72, 82 and 19 on the other hand.
  • the solenoid valve 72 then being open and the solenoid valve 82 for venting being closed, the liquid taken from the bottom of the tank 5 by the coil 53 vaporizes and spreads in the tank 5 above the surface free of liquid nitrogen.
  • the vapor pressure thus established in the tank 5 is limited by the pressure regulator 62, to a pressure of 1.1 bar for example.
  • the control means open the solenoid valve 82 to drop the pressure to the predetermined level.
  • liquid nitrogen contained in the tank 5 is expelled in the circuit 1, through the valve 18.
  • the nitrogen spreads in the circuit by bathing the products placed in tank 2.
  • part of the liquid vaporizes and disperses in the atmosphere.
  • the non-vaporized part flows to a funnel 21 connected by a line 14, and through the normally open solenoid valve 15, to the recovery tank 4 which then gradually fills while the tank 5 is emptied.
  • the control means control the level of the liquid in the tank 4. If that -this is higher than a predetermined low level, corresponding here too and for the same reasons, for example to a quarter of the maximum capacity of the tank 4, the control means trigger a pressurization of this tank by opening the solenoid valve 71 and by closing the 81 venting solenoid valve.
  • Liquid withdrawn by the coil 43 from the bottom of the tank 4 then vaporizes and the vapor pressure above the liquid increases to a value set by the pressure regulator 61, to a value slightly higher than the set value (1.1 bar) fixed for the pressure in the tank 5, i.e. 1.2 bar for example.
  • the pressure switch 111 signals this pressure level to the control means.
  • the pressure in the tank 5 is constantly maintained at a value higher than atmospheric pressure whereas this is not the case in the tank 4 where the solenoid valve 81 for venting is normally open to allow the filling of the tank 4 with nitrogen at atmospheric pressure recovered at the outlet of tank 2.
  • the control means of the device trigger the opening of the solenoid valve 17 and the closing of the solenoid valve 15.
  • a stream of liquid nitrogen then exits of the reservoir 4 to fill the reservoir 5 which, by assumption as we saw above, then reached its low level.
  • the level of nitrogen in the tank 5 then increases constantly to the maximum filling level of this tank or, according to the invention, until the level of nitrogen in the tank 4 reaches its low level.
  • the control means close the solenoid valve 17 to prevent the reservoir 4 from being excessively emptied. There is then reopening of the solenoid valves 14 and 81 to allow the tank 4 to fill again.
  • the reservoir 5 is not filled, there is opening of the solenoid valve 19 to complete the filling of the reservoir 5 with liquid nitrogen coming from the external source 20.
  • This liquid can then also enter directly into circuit 1, the valve 18 then being open.
  • the reservoir 20 also serves to recharge the circuit so as to compensate for the losses by evaporation of liquid nitrogen in the tank 2.
  • the process described above is repeated periodically so that the reservoir 5 is constantly filled with a sufficient quantity of pressurized liquid nitrogen, suitable for supplying the circuit 1 with a substantially constant flow rate.
  • the electronic control means selectively initiate transfers of liquid nitrogen from the reservoir to the reservoir 5, from the source 20 to this reservoir, and from the supplies to the reservoir 4 by the output of the circuit 1 so as to maintain predetermined relationships between the levels of liquid nitrogen in the two tanks, these relationships being necessary to ensure a smooth supply of circuit 1 and the recycling of the nitrogen circulating in this circuit.
  • the device according to the invention is thus particularly well suited to the freezing of pharmaceutical products, subject to particularly strict standards of cleanliness.
  • cryogenic products such as liquid argon could be used and other applications envisaged: temperature conditioning of a gas such as air, etc.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

The device supplies a circuit (1) comprising a section at ambient pressure, such as a tray (2) for freezing food, pharmaceutical or veterinary products. It comprises a) a first tank (4) which is for recovering the liquid and is fitted with means (43,61,71,81) for pressurising the liquid collected, b) a second tank (5) which is constantly pressurised and operates to supply the circuit (1) with pressurised cryogenic liquid, this second tank being in selective fluid communication (16) with the first tank, and c) means (12) which are sensitive to a predetermined relationship between the levels of filling of the two tanks, for selectively activating the pressurisation means (43,61,71,81) of the first tank (4) so as to transfer cryogenic liquid contained in the first tank into the second tank (5). <IMAGE>

Description

La présente invention est relative à un dispositif de recyclage d'un liquide cryogénique et, plus particulièrement, à un tel dispositif conçu pour alimenter un circuit comprenant au moins une section sensiblement à la pression ambiante, typiquement à l'air libre, telle qu'on en trouve dans une application de l'invention à la congélation de produits alimentaires, pharmaceutiques ou vétérinaires.The present invention relates to a device for recycling a cryogenic liquid and, more particularly, to such a device designed to supply a circuit comprising at least one section substantially at ambient pressure, typically in the open air, such as they are found in an application of the invention to the freezing of food, pharmaceutical or veterinary products.

On a récemment proposé de procéder à la congélation de produits, notamment alimentaires, en disposant les produits dans un courant d'azote liquide, à l'intérieur d'un tunnel dit de "croutage" où l'azote liquide circule à la pression atmosphérique. La circulation de l'azote liquide dans le tunnel et son recyclage dans le circuit d'alimentation de celui-ci sont assurés par des pompes. On connaît de la demande de brevet EP-A-505.222 un dispositif de congélation de ce type.It has recently been proposed to freeze products, especially food, by placing the products in a stream of liquid nitrogen, inside a so-called "crusting" tunnel where the liquid nitrogen circulates at atmospheric pressure. . The circulation of liquid nitrogen in the tunnel and its recycling in its supply circuit are ensured by pumps. There is known from patent application EP-A-505,222 a freezing device of this type.

Le passage de l'azote liquide dans des pompes n'est pas sans inconvénient. En effet, des particules diverses, de joints par exemple, ou des gouttes d'huile peuvent se détacher des pompes et polluer ainsi l'azote liquide. Une telle pollution est considérée comme rédhibitoire lorsqu'il s'agit de congeler certains produits, notamment des produits pharmaceutiques.The passage of liquid nitrogen through pumps is not without drawbacks. Indeed, various particles, from seals for example, or drops of oil can detach from the pumps and thus pollute the liquid nitrogen. Such pollution is considered prohibitive when it comes to freezing certain products, in particular pharmaceutical products.

La présente invention a donc pour but de réaliser, de façon simple, souple et efficace, un dispositif de recyclage d'un liquide cryogénique dans un circuit, qui ne soit pas tributaire de pompes pour assurer la circulation du liquide dans le circuit et qui ne provoque aucune pollution de ce liquide.The present invention therefore aims to achieve, in a simple, flexible and efficient manner, a device for recycling a cryogenic liquid in a circuit, which is not dependent on pumps to ensure the circulation of the liquid in the circuit and which does not causes no pollution of this liquid.

La présente invention a aussi pour but de réaliser un tel dispositif qui soit susceptible d'alimenter un circuit comprenant une section sensiblement à la pression atmosphérique telle qu'un tunnel de congélation de produits ou ceux-ci baignent dans un courant du liquide cryogénique.The present invention also aims to provide such a device which is capable of supplying a circuit comprising a section substantially at atmospheric pressure such as a freezing tunnel of products or these are immersed in a stream of cryogenic liquid.

On atteint ces buts de l'invention, ainsi que d'autres qui apparaîtront à la lecture de la description qui va suivre, avec un dispositif de recyclage du type susmentionné comprenant a) un premier réservoir cryogénique pour récupérer ledit liquide à la sortie de ladite section, ce réservoir étant muni de moyens pour pressuriser le liquide recueilli, b) un deuxième réservoir cryogénique constamment pressurisé en fonctionnement et raccordé au circuit en amont de ladite section pour l'alimenter avec du liquide cryogénique pressurisé, ce deuxième réservoir étant en communication sélective de fluide avec le premier réservoir, et c) des moyens sensibles à une relation prédéterminée des niveaux de remplissage des deux réservoirs pour activer sélectivement les moyens de pressurisation du premier réservoir de manière à transférer dans le deuxième réservoir du liquide cryogénique contenu dans le premier réservoir.These objects of the invention are achieved, as well as others which will appear on reading the description which follows, with a recycling device of the above-mentioned type comprising a) a first cryogenic tank. to recover said liquid at the outlet of said section, this tank being provided with means for pressurizing the collected liquid, b) a second cryogenic tank constantly pressurized in operation and connected to the circuit upstream of said section to supply it with cryogenic liquid pressurized, this second tank being in selective fluid communication with the first tank, and c) means sensitive to a predetermined relationship of the filling levels of the two tanks to selectively activate the pressurization means of the first tank so as to transfer into the second reservoir of the cryogenic liquid contained in the first reservoir.

Grâce au transfert de liquide ainsi réalisé entre les premier et deuxième réservoirs, ce dernier peut alimenter le circuit avec du liquide recyclé et repressurisé, ce qui assure la circulation du liquide sans pompe, et donc sans pollution.Thanks to the liquid transfer thus produced between the first and second reservoirs, the latter can supply the circuit with recycled and repressurized liquid, which ensures the circulation of the liquid without pump, and therefore without pollution.

La présente invention concerne également un appareil simple et fiable de congélation de produits comprenant au moins un dispositif tel que défini ci-dessus.The present invention also relates to a simple and reliable apparatus for freezing products comprising at least one device as defined above.

D'autres caractéristiques et avantages de la présente invention apparaîtront à la lecture de la description qui va suivre et à l'examen du dessin annexé dans lequel la figure unique représente schématiquement l'organisation du dispositif suivant l'invention.Other characteristics and advantages of the present invention will appear on reading the description which follows and on examining the appended drawing in which the single figure schematically represents the organization of the device according to the invention.

A titre d'exemple seulement, le dispositif de la figure 1 sert à alimenter, avec un liquide cryogénique tel que de l'azote liquide, un circuit 1 passant par un bac 2 dans lequel trempe des flacons 3₁,3₂,3₃, etc... contenant des produits à congeler, alimentaires, pharmaceutiques ou vétérinaires par exemple. Le dispositif comprend essentiellement des premier et deuxième réservoirs de liquide cryogénique 4 et 5 respectivement, comprenant chacun un récipient à double paroi classique 4₁,4₂, et 5₁,5₂, respectivement. Chaque récipient 4,5 est muni en outre de moyens de pressurisation internes comprenant un serpentin 4₃,5₃, respectivement, installé classiquement entre le fond de la paroi 4₁,5₁ et le col bouché de cette même paroi.By way of example only, the device of FIG. 1 is used to supply, with a cryogenic liquid such as liquid nitrogen, a circuit 1 passing through a tank 2 in which quenching bottles 3₁, 3₂, 3₃, etc. .. containing products to be frozen, food, pharmaceutical or veterinary for example. The device essentially comprises first and second cryogenic liquid tanks 4 and 5 respectively, each comprising a conventional double-walled container 4₁, 4₂, and 5₁, 5₂, respectively. Each container 4,5 is further provided with internal pressurization means comprising a coil 4₃, 5₃, respectively, conventionally installed between the bottom of the wall 4₁, 5₁ and the blocked neck of this same wall.

Sur chaque serpentin 4₃,5₃, on trouve en série, une vanne de régulation de pression 6₁,6₂ et une électrovanne 7₁,7₂, respectivement. Les réservoirs 4,5 sont également équipés d'électrovannes de mise à l'air libre 8₁,8₂, de capteurs de niveau du liquide 9₁,9₂, de manomètres 10₁,10₂ et de pressostats 11₁,11₂ respectivement. Toutes les électrovannes sont commandées par des moyens électroniques contenus dans une armoire 12 qui reçoit les signaux fournis par les pressostats et les capteurs de niveau 9₁,9₂, les niveaux des réservoirs 4,5 pouvant être affichés sur l'armoire en 13₁,13₂, respectivement. Les capteurs de niveau peuvent être du type classique, à canne, ou du type décrit dans la demande de brevet EP-A-530.102.On each coil 4₃, 5₃, there is in series, a pressure regulating valve 6₁, 6₂ and a solenoid valve 7₁, 7 respectivement, respectively. The tanks 4,5 are also equipped with air release solenoid valves 8₁, 8₂, liquid level sensors 9₁, 9₂, pressure gauges 10₁, 10₂ and pressure switches 11₁, 11₂ respectively. All the solenoid valves are controlled by electronic means contained in a cabinet 12 which receives the signals supplied by the pressure switches and the level sensors 9₁, 9₂, the levels of the tanks 4.5 being able to be displayed on the cabinet in 13₁, 13₂, respectively. The level sensors can be of the conventional type, with a rod, or of the type described in patent application EP-A-530,102.

Le réservoir 4 recueille, par un entonnoir 21 et un conduit 14 équipé d'une électrovanne 15 également commandée par l'armoire 12, l'azote liquide à la pression atmosphérique qui sort du bac de congélation 2. L'azote ainsi récupéré peut, dans des conditions que l'on décrira plus loin, être renvoyé dans le réservoir 5, par un conduit 16 équipé d'une électrovanne 17 commandée par les moyens électroniques contenus dans l'armoire 12.The reservoir 4 collects, by a funnel 21 and a conduit 14 equipped with a solenoid valve 15 also controlled by the cabinet 12, the liquid nitrogen at atmospheric pressure which leaves the freezing tank 2. The nitrogen thus recovered can, under conditions which will be described later, be returned to the tank 5, by a conduit 16 equipped with a solenoid valve 17 controlled by the electronic means contained in the cabinet 12.

Le réservoir 5 sert à alimenter le circuit 1, à travers une vanne 18 qui peut être à commande manuelle. Le réservoir est lui-même alimenté, suivant la présente invention, soit par une source extérieure 20, à travers une électrovanne 19, soit par le réservoir 4, comme on l'explique ci-dessous dans la description du fonctionnement du dispositif suivant l'invention. En préambule, on notera que les électrovannes : 7₁,17,8₂,19, sont normalement fermées

Figure imgb0001
8₁,15,7₂, sont normalement ouvertes
Figure imgb0002
 The reservoir 5 is used to supply the circuit 1, through a valve 18 which can be manually controlled. The reservoir is itself supplied, according to the present invention, either by an external source 20, through a solenoid valve 19, or by the reservoir 4, as explained below in the description of the operation of the device according to the invention. In the preamble, it should be noted that the solenoid valves: 7₁, 17.8₂, 19, are normally closed
Figure imgb0001
 8₁, 15.7₂, are normally open
Figure imgb0002

Par ailleurs, le pressostat 11₁ émet un signal lorsque la pression dans le réservoir 4 atteint un niveau prédéterminé autorisant un transfert d'azote sous pression vers le réservoir 5. Le pressostat 11₂ sert à réguler, en permanence, la pression dans le réservoir 5, à un autre niveau prédéterminé. Pour ce faire, le pressostat émet des signaux "haut" et "bas" représentatifs de pressions encadrant ce niveau prédéterminé.Furthermore, the pressure switch 11₁ emits a signal when the pressure in the tank 4 reaches a predetermined level authorizing a transfer of nitrogen under pressure to the tank 5. The pressure switch 11₂ is used to continuously regulate the pressure in the tank 5, at another predetermined level. To do this, the pressure switch emits "high" and "low" signals representative of pressures framing this predetermined level.

Avant de mettre en service le dispositif suivant l'invention, on procède au remplissage du réservoir 5 de distribution d'azote dans le circuit 1. Pour ce faire, les moyens électroniques de commande mettent sous tension les électrovannes 19 et 8₂ (de mise à l'air libre) normalement fermées qui s'ouvrent donc, ainsi que l'électrovanne 7₂ normalement ouverte qui se ferme alors. L'autre réservoir 4 doit être à ce moment inactif, et, pour ce faire, les électrovannes 17,15,7₁ et 8₁ sont maintenues hors tension.Before putting the device according to the invention into service, the nitrogen distribution tank 5 is filled in the circuit 1. To do this, the electronic control means energize the solenoid valves 19 and 8₂ (from normally open air) which therefore open, as does the normally open solenoid valve 7₂ which then closes. The other reservoir 4 must at this time be inactive, and to do this, the solenoid valves 17, 15, 7 and 8 are kept de-energized.

La source extérieure 20 d'azote sous pression, de 1,5 à 2 bars, par exemple, se vide alors dans le réservoir 5 à travers l'électrovanne 19 ouverte, jusqu'à ce que le capteur de niveau 9₂ indique aux moyens électroniques contenus dans l'armoire 12 que le niveau de remplissage maximum du réservoir 5 est atteint.The external source 20 of nitrogen under pressure, from 1.5 to 2 bars, for example, is then emptied into the tank 5 through the open solenoid valve 19, until the level sensor 9₂ indicates to the electronic means contained in the cabinet 12 that the maximum filling level of the reservoir 5 is reached.

Ces moyens électroniques (non représentés) peuvent être aisément constitués à partir de la description des divers modes de fonctionnement du dispositif suivant l'invention qui vont maintenant être décrits. Ils sont renseignés sur l'état du dispositif par les capteurs de niveau 9₁,9₂ et les pressostats 11₁,11₂ et réagissent aux signaux reçus de ces moyens en commandant l'ouverture ou la fermeture des diverses électrovannes, comme indiqué ci-dessous.These electronic means (not shown) can easily be formed from the description of the various modes of operation of the device according to the invention which will now be described. They are informed of the state of the device by the level sensors 9₁, 9₂ and the pressure switches 11₁, 11₂ and react to the signals received from these means by controlling the opening or closing of the various solenoid valves, as indicated below.

Le réservoir 5 étant rempli, il est possible de mettre en service le dispositif pour que celui-ci débite dans le circuit 1 l'azote liquide qu'il contient. Pour ce faire, on ouvre la vanne 18 et les moyens de commande mettent ou maintiennent hors tension les électrovannes 8₁,7₁,15,17 d'une part et les électrovannes 7₂,8₂ et 19 d'autre part. L'électrovanne 7₂ étant alors ouverte et l'électrovanne 8₂ de mise à l'air libre étant fermée, du liquide prélevé dans le fond du réservoir 5 par le serpentin 5₃ se vaporise et se répand dans le réservoir 5 au-dessus de la surface libre de l'azote liquide. La pression de vapeur ainsi établie dans le réservoir 5 est limitée par le régulateur de pression 6₂, à une pression de 1,1 bar par exemple. Quand la pression dans le réservoir vient à dépasser le niveau haut du pressostat 11₂, les moyens de commande ouvrent l'électrovanne 8₂ pour faire tomber la pression au niveau prédéterminé.The reservoir 5 being filled, it is possible to put the device into service so that it delivers in the circuit 1 the liquid nitrogen which it contains. To do this, the valve 18 is opened and the control means put or maintain the electrovalves 8₁, 7₁, 15,17 on the one hand and the electrovalves 7₂, 8₂ and 19 on the other hand. The solenoid valve 7₂ then being open and the solenoid valve 8₂ for venting being closed, the liquid taken from the bottom of the tank 5 by the coil 5₃ vaporizes and spreads in the tank 5 above the surface free of liquid nitrogen. The vapor pressure thus established in the tank 5 is limited by the pressure regulator 6₂, to a pressure of 1.1 bar for example. When the pressure in the reservoir comes to exceed the high level of the pressure switch 11₂, the control means open the solenoid valve 8₂ to drop the pressure to the predetermined level.

Grâce à cette légère surpression par rapport à l'atmosphère, de l'azote liquide contenu dans le réservoir 5 est chassé dans le circuit 1, à travers la vanne 18. L'azote se répand dans le circuit en venant baigner les produits disposés dans le bac 2. Dans ce bac, à la pression atmosphérique, une partie du liquide se vaporise et se disperse dans l'atmosphère. La partie non vaporisée s'écoule vers un entonnoir 21 raccordé par une ligne 14, et à travers l'électrovanne 15 normalement ouverte, au réservoir 4 de récupération qui se remplit alors progressivement tandis que le réservoir 5 se vide.Thanks to this slight overpressure with respect to the atmosphere, liquid nitrogen contained in the tank 5 is expelled in the circuit 1, through the valve 18. The nitrogen spreads in the circuit by bathing the products placed in tank 2. In this tank, at atmospheric pressure, part of the liquid vaporizes and disperses in the atmosphere. The non-vaporized part flows to a funnel 21 connected by a line 14, and through the normally open solenoid valve 15, to the recovery tank 4 which then gradually fills while the tank 5 is emptied.

Ce processus se poursuit jusqu'à ce que le niveau de l'azote dans le réservoir 5 tombe à un niveau bas prédéterminé, correspondant par exemple au quart de la contenance maximum du réservoir. De l'azote liquide doit en effet rester en permanence dans le réservoir de manière à éviter que celui-ci ne se réchauffe. A la réception d'un signal émis par le capteur de niveau 9₂ et représentatif du fait que le niveau de l'azote dans le réservoir a atteint ledit niveau bas, les moyens de commande contrôlent le niveau du liquide dans le réservoir 4. Si celui-ci est supérieur à un niveau bas prédéterminé, correspondant ici aussi et pour les mêmes raisons, par exemple au quart de la contenance maximum du réservoir 4, les moyens de commande déclenchent une mise en pression de ce réservoir en ouvrant l'électrovanne 7₁ et en fermant l'électrovanne 8₁ de mise à l'air libre. Du liquide prélevé par le serpentin 4₃ dans le fond du réservoir 4 se vaporise alors et la pression de vapeur au-dessus du liquide croît jusqu'à une valeur fixée par le régulateur de pression 6₁, à une valeur légèrement supérieure à la valeur de consigne (1,1 bar) fixée pour la pression dans le réservoir 5, soit 1,2 bar par exemple. Le pressostat 11₁ signale ce niveau de pression aux moyens de commande.This process continues until the level of nitrogen in the tank 5 falls to a predetermined low level, corresponding for example to a quarter of the maximum capacity of the tank. Liquid nitrogen must remain permanently in the tank in order to prevent it from heating up. On reception of a signal emitted by the level sensor 9₂ and representative of the fact that the level of nitrogen in the tank has reached said low level, the control means control the level of the liquid in the tank 4. If that -this is higher than a predetermined low level, corresponding here too and for the same reasons, for example to a quarter of the maximum capacity of the tank 4, the control means trigger a pressurization of this tank by opening the solenoid valve 7₁ and by closing the 8₁ venting solenoid valve. Liquid withdrawn by the coil 4₃ from the bottom of the tank 4 then vaporizes and the vapor pressure above the liquid increases to a value set by the pressure regulator 6₁, to a value slightly higher than the set value (1.1 bar) fixed for the pressure in the tank 5, i.e. 1.2 bar for example. The pressure switch 11₁ signals this pressure level to the control means.

On notera à cet égard que, suivant l'invention, la pression dans le réservoir 5 est constamment maintenue à une valeur supérieure à la pression atmosphérique alors que ce n'est pas le cas dans le réservoir 4 où l'électrovanne 8₁ de mise à l'air libre est normalement ouverte pour permettre le remplissage du réservoir 4 par l'azote à la pression atmosphérique récupéré à la sortie du bac 2.It will be noted in this regard that, according to the invention, the pressure in the tank 5 is constantly maintained at a value higher than atmospheric pressure whereas this is not the case in the tank 4 where the solenoid valve 8₁ for venting is normally open to allow the filling of the tank 4 with nitrogen at atmospheric pressure recovered at the outlet of tank 2.

Quand la pression dans le réservoir 4 atteint la valeur de consigne fixée, les moyens de commande du dispositif suivant l'invention déclenchent l'ouverture de l'électrovanne 17 et la fermeture de l'électrovanne 15. Un courant d'azote liquide sort alors du réservoir 4 pour remplir le réservoir 5 qui, par hypothèse comme on l'a vu plus haut, a alors atteint son niveau bas. Le niveau de l'azote dans le réservoir 5 croît alors constamment jusqu'au niveau de remplissage maximum de ce réservoir ou, suivant l'invention, jusqu'à ce que le niveau de l'azote dans le réservoir 4 atteigne son niveau bas. Dans ce dernier cas, les moyens de commande ferment l'électrovanne 17 pour éviter que le réservoir 4 ne se vide exagérément. Il y a alors réouverture des électrovannes 14 et 8₁ pour permettre au réservoir 4 de se remplir de nouveau.When the pressure in the reservoir 4 reaches the set target value, the control means of the device according to the invention trigger the opening of the solenoid valve 17 and the closing of the solenoid valve 15. A stream of liquid nitrogen then exits of the reservoir 4 to fill the reservoir 5 which, by assumption as we saw above, then reached its low level. The level of nitrogen in the tank 5 then increases constantly to the maximum filling level of this tank or, according to the invention, until the level of nitrogen in the tank 4 reaches its low level. In the latter case, the control means close the solenoid valve 17 to prevent the reservoir 4 from being excessively emptied. There is then reopening of the solenoid valves 14 and 8₁ to allow the tank 4 to fill again.

Si au moment de la fermeture de l'électrovanne 17, le réservoir 5 n'est pas rempli, il y a ouverture de l'électrovanne 19 pour compléter le remplissage du réservoir 5 avec de l'azote liquide venu de la source extérieure 20. Ce liquide peut alors aussi entrer directement dans le circuit 1, la vanne 18 étant alors ouverte. On observera à cet égard que le réservoir 20 sert aussi à recharger le circuit de manière à compenser les pertes par évaporation d'azote liquide dans le bac 2.If at the time of closing of the solenoid valve 17, the reservoir 5 is not filled, there is opening of the solenoid valve 19 to complete the filling of the reservoir 5 with liquid nitrogen coming from the external source 20. This liquid can then also enter directly into circuit 1, the valve 18 then being open. In this respect, it will be observed that the reservoir 20 also serves to recharge the circuit so as to compensate for the losses by evaporation of liquid nitrogen in the tank 2.

Le processus décrit ci-dessus se répète périodiquement de manière que le réservoir 5 soit constamment rempli d'une quantité suffisante d'azote liquide sous pression, propre à alimenter le circuit 1 avec un débit sensiblement constant. Ainsi, les moyens électroniques de commande déclenchent-ils sélectivement des transferts d'azote liquide du réservoir vers le réservoir 5, de la source 20 vers ce réservoir, et des alimentations du réservoir 4 par la sortie du circuit 1 de manière à maintenir des relations prédéterminées entre les niveaux de l'azote liquide dans les deux réservoirs, ces relations étant nécessaires pour assurer une alimentation sans à-coup du circuit 1 et le recyclage de l'azote circulant dans ce circuit.The process described above is repeated periodically so that the reservoir 5 is constantly filled with a sufficient quantity of pressurized liquid nitrogen, suitable for supplying the circuit 1 with a substantially constant flow rate. Thus, the electronic control means selectively initiate transfers of liquid nitrogen from the reservoir to the reservoir 5, from the source 20 to this reservoir, and from the supplies to the reservoir 4 by the output of the circuit 1 so as to maintain predetermined relationships between the levels of liquid nitrogen in the two tanks, these relationships being necessary to ensure a smooth supply of circuit 1 and the recycling of the nitrogen circulating in this circuit.

Il apparaît maintenant que l'invention permet bien d'atteindre les objectifs annoncés, à savoir : assurer une circulation d'un courant d'azote liquide sans pompe et donc sans pollution. Le dispositif suivant l'invention est ainsi particulièrement bien adapté à la congélation de produits pharmaceutiques, soumise à des normes de propreté particulièrement sévères.It now appears that the invention does indeed achieve the stated objectives, namely: ensuring the circulation of a stream of liquid nitrogen without a pump and therefore without pollution. The device according to the invention is thus particularly well suited to the freezing of pharmaceutical products, subject to particularly strict standards of cleanliness.

Bien entendu l'invention n'est pas limitée au mode de réalisation décrit et représenté qui n'a été donné qu'à titre d'exemple. D'autres produits cryogéniques tels que l'argon liquide pourraient être utilisés et d'autres applications envisagées : conditionnement en température d'un gaz tel que l'air, etc...Of course, the invention is not limited to the embodiment described and shown which has been given only by way of example. Other cryogenic products such as liquid argon could be used and other applications envisaged: temperature conditioning of a gas such as air, etc.

Claims (7)

Dispositif de recyclage d'un liquide cryogénique dans un circuit (1) comprenant au moins une section (2) sensiblement à la pression ambiante, caractérisé en ce qu'il comprend : a) un premier réservoir cryogénique (4) pour récupérer ledit liquide à la sortie de ladite section, ce réservoir étant muni de moyens (4₃,6₁,7₁,8₁) pour pressuriser le liquide recueilli, b) un deuxième réservoir cryogénique (5) constamment pressurisé en fonctionnement et raccordé au circuit (1) en amont de ladite section (2) à l'air libre pour l'alimenter avec du liquide cryogénique pressurisé, ce deuxième réservoir étant en communication sélective de fluide (16) avec le premier réservoir, et c) des moyens (12) sensibles à une relation prédéterminée des niveaux de remplissage des deux réservoirs pour activer sélectivement les moyens de pressurisation (4₃,6₁,7₁,8₁) du premier réservoir (4) de manière à transférer dans le deuxième réservoir (5) du liquide cryogénique contenu dans le premier réservoir. Device for recycling a cryogenic liquid in a circuit (1) comprising at least one section (2) substantially at ambient pressure, characterized in that it comprises: a) a first cryogenic tank (4) for recovering said liquid at the outlet of said section, this tank being provided with means (4₃, 6₁, 7₁, 8₁) for pressurizing the collected liquid, b) a second cryogenic tank (5) constantly pressurized in operation and connected to the circuit (1) upstream of said section (2) in the open air to supply it with pressurized cryogenic liquid, this second tank being in selective communication fluid (16) with the first reservoir, and c) means (12) sensitive to a predetermined relationship of the filling levels of the two tanks for selectively activating the pressurization means (4₃, 6₁, 7₁, 8₁) of the first tank (4) so as to transfer into the second tank ( 5) cryogenic liquid contained in the first tank. Dispositif selon la revendication 1, caractérisé en ce que le deuxième réservoir (5) est sélectivement connectable à une source extérieure (20) de liquide cryogénique, lesdits moyens (12) sensibles à une relation prédéterminée des niveaux de remplissage des deux réservoirs commandant sélectivement l'alimentation du deuxième réservoir (5) par cette source (20) quand le niveau du liquide dans le premier réservoir atteint un niveau bas prédéterminé.Device according to claim 1, characterized in that the second tank (5) is selectively connectable to an external source (20) of cryogenic liquid, said means (12) sensitive to a predetermined relationship of the filling levels of the two tanks selectively controlling the supply of the second reservoir (5) by this source (20) when the level of the liquid in the first reservoir reaches a predetermined low level. Dispositif selon l'une des revendications 1 et 2, caractérisé en ce que lesdits moyens (12) sensibles à une relation prédéterminée des niveaux de remplissage des deux réservoirs commandent le vidage du premier (4) dans le deuxième (5) jusqu'à ce que soit atteint soit un niveau maximum prédéterminé dans le deuxième réservoir (5), soit un niveau minimum prédéterminé dans le premier réservoir (4).Device according to one of claims 1 and 2, characterized in that said means (12) sensitive to a predetermined relationship of the filling levels of the two tanks control the emptying of the first (4) into the second (5) until that either a predetermined maximum level in the second tank (5) is reached, or a predetermined minimum level in the first tank (4). Dispositif selon l'une des revendications 1 à 3, caractérisé en ce qu'au moins un des réservoirs (4,5) est muni de moyens de pressurisation internes.Device according to one of claims 1 to 3, characterized in that at least one of the tanks (4,5) is provided with internal pressurization means. Dispositif selon l'une des revendications 1 à 4, caractérisé en ce que le liquide cryogénique est de l'azote liquide.Device according to one of claims 1 to 4, characterized in that the cryogenic liquid is liquid nitrogen. Application du dispositif selon l'une des revendications 1 à 5, à la congélation de produits disposés dans ladite section (2) du circuit.Application of the device according to one of claims 1 to 5, to the freezing of products placed in said section (2) of the circuit. Appareil de congélation, comprenant une section (1) d'acheminement de produits comportant une sortie de liquide cryogénique, caractérisé en ce qu'il comprend un dispositif selon l'une des revendications précédentes.Freezing apparatus, comprising a section (1) for conveying products comprising an outlet for cryogenic liquid, characterized in that it comprises a device according to one of the preceding claims.
EP94400456A 1993-03-26 1994-03-03 Cryogenic liquid recycling device and its application in a product freezing apparatus Withdrawn EP0617247A1 (en)

Applications Claiming Priority (2)

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FR9303480 1993-03-26
FR9303480A FR2703139B1 (en) 1993-03-26 1993-03-26 Device for recycling a cryogenic liquid and its application to the freezing of products.

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EP (1) EP0617247A1 (en)
JP (1) JPH06300409A (en)
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FR2703139A1 (en) 1994-09-30
US5419140A (en) 1995-05-30
BR9401303A (en) 1995-03-28
JPH06300409A (en) 1994-10-28

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