EP1652574A2 - Process and apparatus for the preparation of a composite-type solid propellant paste - Google Patents

Process and apparatus for the preparation of a composite-type solid propellant paste Download PDF

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Publication number
EP1652574A2
EP1652574A2 EP05292264A EP05292264A EP1652574A2 EP 1652574 A2 EP1652574 A2 EP 1652574A2 EP 05292264 A EP05292264 A EP 05292264A EP 05292264 A EP05292264 A EP 05292264A EP 1652574 A2 EP1652574 A2 EP 1652574A2
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EP
European Patent Office
Prior art keywords
fraction
extracted
paste
kneader
kneaded
Prior art date
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Withdrawn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
EP05292264A
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German (de)
French (fr)
Other versions
EP1652574A3 (en
Inventor
Marie Gaudre
Christine Marraud
Eric Giraud
Eric Marchand
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.)
Eurenco SA
Safran Ceramics SA
Original Assignee
Eurenco SA
SNPE Materiaux Energetiques SA
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Application filed by Eurenco SA, SNPE Materiaux Energetiques SA filed Critical Eurenco SA
Publication of EP1652574A2 publication Critical patent/EP1652574A2/en
Publication of EP1652574A3 publication Critical patent/EP1652574A3/en
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/50—Mixing liquids with solids
    • B01F23/57—Mixing high-viscosity liquids with solids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/50—Mixing liquids with solids
    • B01F23/53—Mixing liquids with solids using driven stirrers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
    • B01F25/50—Circulation mixers, e.g. wherein at least part of the mixture is discharged from and reintroduced into a receptacle
    • B01F25/53—Circulation mixers, e.g. wherein at least part of the mixture is discharged from and reintroduced into a receptacle in which the mixture is discharged from and reintroduced into a receptacle through a recirculation tube, into which an additional component is introduced
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/80—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis
    • B01F27/90—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis with paddles or arms 
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F35/00—Accessories for mixers; Auxiliary operations or auxiliary devices; Parts or details of general application
    • B01F35/90—Heating or cooling systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F35/00—Accessories for mixers; Auxiliary operations or auxiliary devices; Parts or details of general application
    • B01F35/90—Heating or cooling systems
    • B01F2035/99—Heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F2215/00—Auxiliary or complementary information in relation with mixing
    • B01F2215/04—Technical information in relation with mixing
    • B01F2215/0413—Numerical information
    • B01F2215/0436—Operational information
    • B01F2215/0472—Numerical temperature values

Definitions

  • the subject of the present invention is a process for preparing a composite propellant paste and a device that is suitable for carrying out said method.
  • the method and device are improvements to the existing method and device to date.
  • the invention finds particular application in the field of the manufacture of solid propellant loadings for space launcher, strategic and / or tactical.
  • a composite type solid propellant comprises a solid polymeric matrix or binder, powdery solid fillers (oxidizing, optionally reducing and / or energetic) and various additives.
  • the binder is prepared from a liquid resin, having chemically reactive terminations, capable of being crosslinked by at least one also liquid crosslinking agent.
  • the various ingredients of the propellant and the crosslinking agent are introduced into the liquid resin in an appropriate order.
  • the resin by hardening (by crosslinking) by baking at a temperature compatible with the presence of pyrotechnic materials, coats all the ingredients and in particular the powdery fillers to form a solid body.
  • the process currently used to manufacture blocks of such propellants is a batch process, called "batch", consisting of preparing a quantity of product in several kneaded and poured in one or more loads.
  • a first step the various ingredients are introduced into a kneader in a proper order and carefully and long kneaded, under pressure conditions (usually vacuum) and very precise temperature.
  • the mixture which is in the form of a highly viscous paste is poured into a mold, with shaping tools. The whole is baked to ensure the hardening of the dough.
  • the mold is in some cases the same envelope of the propellant, envelope that is properly prepared for carrying out the loading.
  • the mixing phase of highly viscous paste is essential for the quality of the finished product. It is a long and expensive phase by the immobilized material and the consumed energy.
  • a first problem to be solved is to develop a composite propellant paste mixing process, in which the mixing time is reduced without altering the quality of the finished product.
  • Another problem to be solved is to be able to use, if necessary, sensitive charges (for example charges that could to react very violently, to detonate, for low stresses (very low drop height (a few cm), low friction)) without substantial modification of the kneading process, and therefore without increasing cost and risk.
  • sensitive charges for example charges that could to react very violently, to detonate, for low stresses (very low drop height (a few cm), low friction)
  • an improvement is proposed to the mixing phase of the process for preparing a composite propellant paste.
  • Said improvement is based on the implementation of a heat exchange on at least a fraction of the dough (being kneaded) put into external circulation.
  • the invention relates to a process for preparing a propellant paste based on a binder containing solid charges (composite propellant paste).
  • Said method in a conventional manner, comprises successively the introduction into a kneader of the constituent ingredients of said dough and then kneading, in said kneader, under conditions of adequate temperature and pressure, the dough constituted.
  • a fraction of the kneaded pulp (or even several fractions thereof) is (are) circulated, in a loop, outside the kneader and undergone (ssen) t an exchange at the level of this external circulation loop (of each of these external circulation loops).
  • ssen undergone
  • At least one fraction in this text means “one or more fractions” but does not cover the one-time extraction of all the pulp, the entire mixer. Of course, it is not excluded that, by fraction, the entire load of the mixer is concerned with the release.
  • a single dough fraction is removed, undergoes heat exchange and returns to the mixer, cooled or reheated.
  • the process of the invention can be used to prepare propellant pastes containing more or less sensitive powdery solid charges.
  • said process may comprise the introduction into the kneader of solid powder charges not or little sensitive and / or solid powdery solid charges phlegmatized with at least one phlegmatizing fluid.
  • phlegmatizing fluid in the sense of the prior art and the present invention a liquefied gas or, most often, an inert liquid, that is to say not reacting to the previously mentioned solicitations.
  • a sensitive or very sensitive charge is suspended in this liquid, it reacts much less to the stresses and can be handled with much less severe precautions.
  • This process of phlegmatization is known per se.
  • the phlegmatizing fluid is a liquid, this liquid must be a non-solvent for the powdery filler so as not to alter the particle size of said filler; it must also be preferentially non-toxic and non-flammable under the conditions of use.
  • a phlegmatizing fluid that may be used, mention may be made of CO 2 , N 2 , acetone, ethyl acetate and hydrofluoroethers.
  • the mass ratio between phlegmatizing fluid and sensitive powdery fillers is generally of the order of 75/25 to 25/75. Knowing that the propellant paste ready for casting may comprise from 65 to 80% by weight of sensitive powdery fillers, there is therefore in general a very large amount of phlegmatizing liquid to eliminate.
  • such a phlegmatizing fluid is generally removed before the charges are introduced into the mixer. It will be seen later that, in the context of the process of the invention, the phlegmatized charges can be introduced directly into the mixer, the phlegmatizing fluid being eliminated in said mixer.
  • At least a fraction of the kneaded paste is extracted from the kneader, reheated, and then re-introduced into said kneader.
  • this first variant - with heating - advantageously comprises the implementation of the heating (at least at the start of mixing) under temperature conditions in which the at least one phlegmatizing fluid is vaporized.
  • These temperature conditions are obviously to be optimized in view of the nature of the phlegmatizing fluid (s) in question and the possible presence of pyrotechnic materials. It is indicated, in no way limiting, that the at least one fraction of milled paste extracted is then advantageously heated to a temperature between 50 ° C and 95 ° C, very advantageously at a temperature between 55 and 80 ° C.
  • At least a fraction of the kneaded paste is extracted from the kneader, cooled, and then reintroduced into said kneader.
  • the at least one fraction of milled paste extracted can thus be cooled to a temperature between 55 ° C and 20 ° C, more generally at a temperature between 55 ° C and 40 ° C.
  • the method of the invention can be implemented firstly according to the first variant and in a second step according to the second variant.
  • the method of the invention does not pose any particular difficulty as to its implementation.
  • the parameters to be managed or even optimized are obviously, for an external circulation loop, the flow rate of the pulp concerned and the intensity of the heat exchange to be implemented. It may be mentioned here, incidentally, that the (the) fraction (s) of pulp is (are) advantageously taken (s), extracted (s), the lower part of the mixing tank, or even the bottom of said tank and reintroduced (s) in the upper part of said tank.
  • the reintroduction operation is generally carried out above the dough mass within the mixer.
  • the invention relates to a device suitable for implementing the method described above.
  • Said device is of the type of those of the prior art, it has been modified, to a lesser extent, to include at least one external circulation loop equipped with at least one heat exchanger.
  • the device of the invention adapted to the preparation of a propellant paste based on a binder containing powdery solid charges comprises a kneader including a kneading tank and means of mixing, means of thermoregulation and depressurization of said vessel and means for introducing the constituent ingredients of the dough, including means for introducing powdery solid charges.
  • said device is of the type of those of the prior art. Characteristically, it comprises in addition at least one external circulation loop equipped with circulation means and at least one heat exchanger. Each loop with its equipment must allow circulation with heat exchange of a fraction of the kneaded dough.
  • each of the outer circulation loops (equipping the outer circulation loop) are obviously adapted to the nature of the dough in question.
  • the circulation means of the pump type are more particularly adapted to the viscosity of said paste.
  • said means comprise a peristaltic pump.
  • the at least one heat exchanger is a static mixer of the jacketed type with forced circulation of heat transfer fluid against the current.
  • a static mixer not only ensures the heating or cooling of the circulating propellant paste, but also makes it possible to improve the homogenization of said paste before it is reintroduced into the mixer tank. This contributes to the good quality of the finished product.
  • the means for introducing powdery solid charges into the mixing tank can be arranged on the tank, independently of any external circulation loop. They are advantageously arranged to open into an external circulation loop, very advantageously arranged, in such a case, downstream of the heat exchanger (s).
  • the means of thermoregulation and depressurization make it possible to control the conditions of temperature and pressure within the kneader.
  • the depressurization means generally provide vacuum, within said mixer. They intervene in fact in the same way as they do in the devices of the prior art but are in addition capable of contributing to the elimination of the phlegmatizing fluid introduced into the mixer (according to the prior art, said fluid was eliminated off the mixer).
  • Said depressurization means is advantageously coupled to a condensing unit. Such a unit intervenes for the recovery of vaporized phlegmatized fluids, possibly introduced with the pulverulent solid charges.
  • the outer loop (s) is (are) advantageously arranged (s) to ensure a flow from a lower part of the tank, or even the bottom of said tank, to the top of said tank.
  • (the) said (s) loop (s) leads (nt) generally in the upper part, above the filling level provided for said vessel.
  • Figure 1 shows schematically an alternative embodiment of a device of the invention.
  • FIG. 2 represents the cooling rate of an inert propellant paste prepared according to the method of the invention.
  • FIG. 2 is to be considered with Comparative Examples 1a and 1b as well as Examples 2a and 2b of the invention, given below.
  • FIG. 1 there is shown in 1 a jacketed type of mixer in which circulates a heat transfer fluid that can be heated or cool at will, such as glycol water; at 10, the vessel of said mixer 1; at 12 and 12a, kneading means, more precisely vertical blades, secured to the cover of the kneader 1 and driven by a motor 11; at 14, thermoregulation means able to control the temperature of the tank 10; at 16, depressurization means able to control the pressure (vacuum or low pressure) of said tank 10.
  • a condensation unit 17 is coupled capable of allowing the recovery of a phlegmatizing fluid, in the hypothesis where such a phlegmatizing fluid intervenes.
  • the tank 10 of the kneader 1 is associated with an external circulation loop 20 equipped with circulation means, a pump 22, and a heat exchanger 30.
  • the temperature of the coolant circulating in said heat exchanger 30, is regulated via the thermal group 32.
  • the outer circulation loop 20 has at its reintroduction mouth a tube 24 equipped with a grid 26.
  • a grid 26 is advantageously used to prevent the entry of foreign bodies and to promote the degassing of the reintroduced paste, by sharing the flow of said dough in thin threads.
  • a hopper for the introduction of powdery solid charges.
  • Said hopper 18 opens into the circulation loop 20, downstream of the heat exchanger 30.
  • the open mixer 1, the liquid binder, the reducing charges (for example aluminum powder), the various additives except the crosslinking agent and the crosslinking catalyst, and the oxidizing charges are introduced beforehand into the tank 10. for example ammonium perchlorate.
  • the kneader 1 is closed and the ingredients are mixed and heated to about 70 ° C (for this purpose, the coolant of the tank is heated to about 80 ° C); vacuuming (or low pressure) allows the mixture to be degassed.
  • the powdery oxidizing charge is introduced via the hopper 18: the heating makes it possible to compensate for the increase in viscosity due to the introduction of the pulverulent fillers.
  • the kneading and homogenization of the dough is then continued (it is generally intended to bring said homogenized dough to a temperature between 20 ° C. and 80 ° C., preferably between 50 ° C. and 65 ° C.).
  • Said paste is then cooled (for this purpose, the coolant of the tank is heated to about 30 ° C), to the casting temperature, about 50 ° C.
  • the crosslinking agent and the crosslinking catalyst are then introduced, still through the hopper 18, before casting after a last homogenization sequence.
  • the temperature of the tank 10 of the kneader 1 is controlled by the means 14; the pressure by the depressurization system 16.
  • At least one of the above heating and cooling steps is improved by extracting a flow of dough from the bottom of the vessel 1, circulating it in the loop 20 with heating or cooling (effective) at the heat exchanger 30 and reintroducing it, warmed or cooled, in the upper part of the tank 1 (above the level of the dough body surface).
  • the reheating in question may be a simple reheating or may also help to effectively extract a phlegmatizing fluid introduced with phlegmatized sensitive powdery solid charges.
  • Comparative Examples 1a and 1b Cooling according to a conventional method
  • the inert propellant paste obtained above is cooled in the mixer by circulation of coolant at 40 ° C in the jacket of the tank of the kneader.
  • the tank is under vacuum (about 5 mm Hg), and the speed of rotation of the blades is 5 rpm.
  • the temperature of the dough at the bottom of the tank is measured during the cooling step.
  • the cooling of the propellant paste takes place over 12 minutes (eg Comp. and the cooling from 70 ° C. to 55 ° C. is carried out in 13 to 14 minutes (eg Comp 1b).
  • the same propellant paste as that prepared above is cooled according to the method of the invention.
  • the operating conditions of the kneader are identical to those of the two preceding comparative examples. But, for the cooling phase, the propellant paste is taken at the bottom of the tank via a peristaltic pump, passes into a heat exchanger and is reinjected into the mixer tank according to the diagram shown in Figure 1; for these tests, the device comprises a single external circuit.
  • the peristaltic pump is a pump type ABAQUE ALO type, whose flow varies between 250 kg / h and 150 kg / h depending on the increasing viscosity of the dough when it cools and its temperature decreases about 70 ° C at about 45 ° C.
  • the heat exchanger consists of a SULZER static mixer type SMXL 30 mm in diameter and 800 mm in length; it comprises a double wall with circulation of a heat transfer fluid at 30 ° C for Example 2a and at 20 ° C for Example 2b.
  • the temperature of the propellant paste is measured at the bottom of the tank during the cooling step. For two separate kneaded kneads, the results are shown in Table 2 and shown in Figure 2. ⁇ u> Table 2 ⁇ / u> T initial dough Heat transfer fluid exchanger V cooling Ex. 2a 66 ° C 30 ° C 1.75 ° C / min Ex. 2b 69 ° C 20 ° C 3 ° C / min
  • the implementation of the method of the invention allows to cool the propellant paste from 66 ° C to 55 ° C in about 6 min. (Ex 2a), and 69 ° C to 55 ° C in 5 min (Ex 2b).
  • the cooling rate is thus doubled (eg 2a v. Ex .: Comp 1a) or tripled (eg 2b v. Ex Comp 1b).
  • a sensitive charge (hexogen) is phlegmatized by mixing 1.5 kg of said sensitive charge with 4.5 kg of a liquid hydrofluoroether, marketed under the name HFE 7100 by the company 3M.
  • HFE 7100 The boiling point of HFE 7100 is 61 ° C at atmospheric pressure; moreover, this product is neither carcinogenic nor mutagenic and is not harmful for reproduction (non-CMR). Finally it is not flammable in these conditions of use.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Dispersion Chemistry (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)

Abstract

The procedure consists of introducing the propergol paste ingredients - a bonding agent and powdered solids - into a mixer (1), and mixing them in suitable conditions of pressure and temperature. During the mixing process a fraction of the paste is extracted from the mixer, subjected to thermal exchange, and returned to the mixer. The powdered solids include charges that have little or no sensitivity and/or charges that are phlegmatised by a fluid. The extracted fraction is either reheated to a preferable temperature of 55 - 80 degrees C, with the vaporised phlegmatising fluid recuperated, or cooled at a preferable temperatutre of 55 - 40 degrees C. The apparatus used for the process comprises a mixer with a chamber (10) and mixing elements (12, 12bis), a temperature regulator (14), a depressuriser (16), and a system (18) for introducing the solid charges. It differs in that it includes an exterior loop (20) with a peristaltinc circulating pump (22) and a thermal exchanger (30).

Description

La présente invention a pour objet un procédé de préparation d'une pâte de propergol de type composite ainsi qu'un dispositif convenant à la mise en oeuvre dudit procédé.The subject of the present invention is a process for preparing a composite propellant paste and a device that is suitable for carrying out said method.

Lesdits procédé et dispositif constituent des améliorations aux procédé et dispositif existants à ce jour.The method and device are improvements to the existing method and device to date.

L'invention trouve notamment application dans le domaine de la fabrication de chargements de propergol solide pour lanceur spatial, stratégique et/ou tactique.The invention finds particular application in the field of the manufacture of solid propellant loadings for space launcher, strategic and / or tactical.

Un propergol solide de type composite comprend une matrice polymérique solide ou liant, des charges solides pulvérulentes (oxydantes, éventuellement réductrices et/ou énergétiques) ainsi que divers additifs.A composite type solid propellant comprises a solid polymeric matrix or binder, powdery solid fillers (oxidizing, optionally reducing and / or energetic) and various additives.

Le liant est préparé à partir d'une résine liquide, présentant des terminaisons chimiquement réactives, susceptible d'être réticulée par au moins un réticulant lui aussi liquide. On introduit dans la résine liquide, suivant un ordre approprié, les différents ingrédients du propergol, puis le réticulant. La résine en durcissant (en réticulant) par une cuisson à une température compatible avec la présence de matériaux pyrotechniques, enrobe tous les ingrédients et notamment les charges pulvérulentes pour former un corps solide.The binder is prepared from a liquid resin, having chemically reactive terminations, capable of being crosslinked by at least one also liquid crosslinking agent. The various ingredients of the propellant and the crosslinking agent are introduced into the liquid resin in an appropriate order. The resin by hardening (by crosslinking) by baking at a temperature compatible with the presence of pyrotechnic materials, coats all the ingredients and in particular the powdery fillers to form a solid body.

On trouve par exemple dans DAVENAS "Technologie des propergols solides", chapitres 10 et 11, Ed. Masson 1989, plus de détails sur les différents ingrédients entrant dans la composition des propergols de type composite.For example, in DAVENAS "Technology of solid propellants", chapters 10 and 11, Ed. Masson 1989, more details on the various ingredients in the composition of composite type propellants are found.

Le procédé actuellement utilisé pour fabriquer des blocs de tels propergols est un procédé discontinu, dit par "batch", consistant à préparer une certaine quantité de produit en plusieurs malaxées et à les couler dans un seul ou plusieurs chargements.The process currently used to manufacture blocks of such propellants is a batch process, called "batch", consisting of preparing a quantity of product in several kneaded and poured in one or more loads.

Dans une première étape, les différents ingrédients sont introduits dans un malaxeur selon un ordre approprié et soigneusement et longuement malaxés, dans des conditions de pression (en général le vide) et de température bien précises. Pour l'étape suivante, le mélange qui se présente sous forme d'une pâte très visqueuse est coulé dans un moule, avec des outillages de mise en forme. L'ensemble subit une cuisson pour assurer le durcissement de la pâte. Le moule constitue dans certains cas l'enveloppe même du propulseur, enveloppe qui est convenablement préparée pour la réalisation du chargement.In a first step, the various ingredients are introduced into a kneader in a proper order and carefully and long kneaded, under pressure conditions (usually vacuum) and very precise temperature. For the next step, the mixture which is in the form of a highly viscous paste is poured into a mold, with shaping tools. The whole is baked to ensure the hardening of the dough. The mold is in some cases the same envelope of the propellant, envelope that is properly prepared for carrying out the loading.

Pour la fabrication de gros chargements, de quelques dizaines à quelques centaines de tonnes, utilisés en général dans le domaine spatial (accélérateurs accolés au lanceur) ou stratégique, il faut enchaîner plusieurs malaxées-coulées dans la même enveloppe. L'enchaînement des malaxées et des coulées doit être rapide, précis et rigoureux.For the manufacture of large loads, from a few tens to a few hundred tons, generally used in space (accelerators contiguous to the launcher) or strategic, we must chain several kneaded-cast in the same envelope. The sequence of kneaded and poured must be fast, precise and rigorous.

La phase de malaxage de pâte très visqueuse est essentielle pour la qualité du produit fini. C'est une phase longue et coûteuse par le matériel immobilisé et l'énergie consommée.The mixing phase of highly viscous paste is essential for the quality of the finished product. It is a long and expensive phase by the immobilized material and the consumed energy.

La durée de cette phase de malaxage, qui comprend des variations imposées de température (réchauffage puis refroidissement de la pâte) s'explique :

  • d'une part, par la difficulté à réaliser un bon mélange, notamment dans le sens vertical (par opposition au sens radial) du malaxeur. La composition renferme des matières très différentes : des granulés, en grande quantité et des liquides, en petites quantités. La pâte résultante présente une forte viscosité ;
  • d'autre part, par la mauvaise qualité des échanges thermiques :
    • la pâte de propergol est un matériau thermiquement peu conducteur (les échanges thermiques sont donc lents) ;
    • la surface d'échange thermique, qui est celle de la cuve du malaxeur, est réduite et de plus une couche solide isolante de pâte se forme sur la paroi.
The duration of this mixing phase, which includes imposed variations in temperature (reheating and cooling of the dough) is explained:
  • firstly, by the difficulty of achieving a good mixture, especially in the vertical direction (as opposed to the radial direction) of the mixer. The composition contains very different materials: granules, in large quantities and liquids, in small quantities. The resulting paste has a high viscosity;
  • on the other hand, by the poor quality of heat exchanges:
    • the propellant paste is a thermally non-conductive material (thermal exchanges are slow);
    • the heat exchange surface, which is that of the mixer tank, is reduced and moreover an insulating solid paste layer is formed on the wall.

Par ailleurs, les contraintes actuelles en matière de fabrication de matériaux énergétiques nécessitent l'utilisation de charges plus sensibles. Or, la mise en oeuvre de ces nouvelles matières premières ne doit pas entraîner une augmentation du coût de fabrication en raison de mesures de sécurité accrues, exigées pour leur manipulation.In addition, the current constraints in the manufacture of energetic materials require the use of more sensitive loads. However, the implementation of these new raw materials must not lead to an increase in the manufacturing cost because of the increased security measures required for their handling.

Ainsi, un premier problème à résoudre consiste à mettre au point un procédé de malaxage de pâte de propergol de type composite, dans lequel la durée de malaxage est réduite sans altération de la qualité du produit fini.Thus, a first problem to be solved is to develop a composite propellant paste mixing process, in which the mixing time is reduced without altering the quality of the finished product.

Un autre problème à résoudre consiste à pouvoir utiliser, si nécessaire, des charges sensibles (par exemple des charges susceptibles de réagir très violemment, jusqu'à détonner, pour de faibles sollicitations (hauteur de chute très faible (quelques cm), de faibles frottement)) sans modification substantielle du procédé de malaxage, et donc sans augmentation de coût et de risque.Another problem to be solved is to be able to use, if necessary, sensitive charges (for example charges that could to react very violently, to detonate, for low stresses (very low drop height (a few cm), low friction)) without substantial modification of the kneading process, and therefore without increasing cost and risk.

Selon l'invention, en référence à ces deux types de problèmes techniques (réduction de la durée du malaxage et intervention de charges sensibles), on propose un perfectionnement à la phase de malaxage du procédé de préparation d'une pâte de propergol de type composite. Ledit perfectionnement est basé sur la mise en oeuvre d'un échange thermique sur au moins une fraction de la pâte (en cours de malaxage) mise en circulation extérieure.According to the invention, with reference to these two types of technical problems (reduction of mixing time and intervention of sensitive charges), an improvement is proposed to the mixing phase of the process for preparing a composite propellant paste. . Said improvement is based on the implementation of a heat exchange on at least a fraction of the dough (being kneaded) put into external circulation.

Ainsi, selon son premier objet, l'invention concerne un procédé de préparation d'une pâte de propergol à base d'un liant renfermant des charges solides (pâte de propergol de type composite). Ledit procédé, de façon classique, comprend successivement l'introduction dans un malaxeur des ingrédients constitutifs de ladite pâte puis le malaxage, dans ledit malaxeur, dans des conditions de température et pression adéquates, de la pâte constituée.Thus, according to its first object, the invention relates to a process for preparing a propellant paste based on a binder containing solid charges (composite propellant paste). Said method, in a conventional manner, comprises successively the introduction into a kneader of the constituent ingredients of said dough and then kneading, in said kneader, under conditions of adequate temperature and pressure, the dough constituted.

De façon caractéristique, en cours dudit procédé de l'invention :

  • au moins une fraction de la pâte malaxée est extraite dudit malaxeur ;
  • ladite au moins une fraction de la pâte malaxée extraite est soumise à un échange thermique ; et
  • ladite au moins une fraction de la pâte malaxée extraite, réchauffée ou refroidie, est réintroduite dans ledit malaxeur.
Characteristically, during said process of the invention:
  • at least a fraction of the kneaded dough is extracted from said kneader;
  • said at least a fraction of the extracted kneaded pulp is subjected to heat exchange; and
  • said at least a fraction of the kneaded pulp extracted, heated or cooled, is reintroduced into said kneader.

En cours du procédé de malaxage, une fraction de la pâte malaxée (voire plusieurs fractions de celle-ci) est(sont) mise(s) à circuler, en boucle, à l'extérieur du malaxeur et subi(ssen)t un échange thermique au niveau de cette boucle de circulation extérieure (de chacune de ces boucles de circulation extérieure). Lorsque plusieurs boucles existent, pour la circulation de différentes fractions de pâte, on a compris qu'elles sont "montées en parallèle" sur le malaxeur.During the kneading process, a fraction of the kneaded pulp (or even several fractions thereof) is (are) circulated, in a loop, outside the kneader and undergone (ssen) t an exchange at the level of this external circulation loop (of each of these external circulation loops). When several loops exist, for the circulation of different pulp fractions, it is understood that they are "connected in parallel" on the mixer.

L'expression "au moins une fraction" signifie dans le présent texte "une ou plusieurs fractions" mais ne couvre pas l'extraction en une seule fois de l'intégralité de la pâte, de l'intégralité de la charge du malaxeur. Bien évidemment, il n'est pas exclu que, par fraction, toute la charge du malaxeur soit concernée par la mise en circulation.The term "at least one fraction" in this text means "one or more fractions" but does not cover the one-time extraction of all the pulp, the entire mixer. Of course, it is not excluded that, by fraction, the entire load of the mixer is concerned with the release.

Selon une variante avantageuse de mise en oeuvre du procédé de l'invention, une unique fraction de pâte est prélevée, subit un échange thermique et retourne dans le malaxeur, refroidie ou réchauffée.According to an advantageous variant of implementation of the process of the invention, a single dough fraction is removed, undergoes heat exchange and returns to the mixer, cooled or reheated.

L'expression "en cours de malaxage" signifie pendant le malaxage mais ne signifie pas forcément au cours du malaxage, c'est-à-dire tout au long dudit malaxage (elle signifie en fait que les étapes de circulation extérieure et chauffage et/ou refroidissement peuvent se produire pendant toute la phase de malaxage ou pendant seulement une partie de celle-ci). En effet, l'homme du métier conçoit d'ores et déjà l'intérêt de réchauffer la pâte (via le concept de l'invention) au démarrage du malaxage (suite à l'introduction des charges, on peut ainsi maîtriser un réchauffement global, visant à diminuer la viscosité, tout en limitant les échauffements locaux), voire lors de celui-ci et de refroidir ladite pâte (via le même concept de l'invention) en fin dudit malaxage (on ne peut en effet couler ou injecter un propergol trop chaud). Ainsi, le procédé de l'invention peut-il être mis en oeuvre selon de nombreuses variantes et notamment :

  • avec circulation et chauffage d'une fraction de la pâte, au démarrage seulement ; ou
  • avec circulation et refroidissement d'une fraction de la pâte en fin de malaxage seulement ; ou
  • avec circulation et chauffage d'une fraction de la pâte au démarrage et avec circulation et refroidissement d'une fraction de la pâte en fin de malaxage...
The term "being kneaded" means during kneading but does not necessarily mean during kneading, i.e. throughout said kneading (it actually means that the steps of outside circulation and heating and / or or cooling may occur during the entire mixing phase or for only part of it). Indeed, the skilled person already conceives the interest of heating the dough (via the concept of the invention) at the start of the mixing (following the introduction of the charges, we can thus control a global warming , aiming at reducing the viscosity, while limiting local heating), or even during it and cooling said dough (via the same concept of the invention) at the end of said mixing (one can not actually sink or inject a propellant too hot). Thus, the method of the invention can be implemented according to many variants and in particular:
  • with circulation and heating of a fraction of the dough, at startup only; or
  • with circulation and cooling of a fraction of the dough at the end of kneading only; or
  • with circulation and heating of a fraction of the dough at the start and with circulation and cooling of a fraction of the dough at the end of mixing ...

Le procédé de l'invention peut être mis en oeuvre pour préparer des pâtes de propergol renfermant des charges solides pulvérulentes plus ou moins sensibles. Ainsi, ledit procédé peut-il comprendre l'introduction dans le malaxeur de charges solides pulvérulentes pas ou peu sensibles et/ou de charges solides pulvérulentes sensibles flegmatisées à l'aide d'au moins un fluide flegmatisant.The process of the invention can be used to prepare propellant pastes containing more or less sensitive powdery solid charges. Thus, said process may comprise the introduction into the kneader of solid powder charges not or little sensitive and / or solid powdery solid charges phlegmatized with at least one phlegmatizing fluid.

L'homme du métier n'ignore pas que si des charges sensibles interviennent dans la fabrication d'un propergol, elles sont manipulées, "incorporées" dans un fluide "flegmatisant". Généralement, un seul fluide de ce type intervient. On n'exclut toutefois nullement l'intervention d'au moins deux fluides de ce type, en mélange.The skilled person is aware that if sensitive charges occur in the manufacture of a propellant, they are manipulated, "incorporated" in a fluid "phlegmatizer". Generally, only one fluid of this type intervenes. However, it does not exclude the intervention of at least two fluids of this type, mixed.

Par fluide flegmatisant, on entend au sens de l'art antérieur et de la présente invention un gaz liquéfié ou, le plus souvent, un liquide inerte, c'est-à-dire ne réagissant pas aux sollicitations précédemment évoquées. Lorsqu'une charge sensible, voire très sensible est mise en suspension dans ce liquide, elle réagit beaucoup moins aux sollicitations et peut être manipulée avec des précautions nettement moins sévères. Ce procédé de flegmatisation est connu en soi. Lorsque le fluide flegmatisant est un liquide, ce liquide doit être un non-solvant pour la charge pulvérulente afin de ne pas altérer la granulométrie de ladite charge ; il doit également être préférentiellement non toxique et non inflammable dans les conditions d'utilisation.By phlegmatizing fluid is meant in the sense of the prior art and the present invention a liquefied gas or, most often, an inert liquid, that is to say not reacting to the previously mentioned solicitations. When a sensitive or very sensitive charge is suspended in this liquid, it reacts much less to the stresses and can be handled with much less severe precautions. This process of phlegmatization is known per se. When the phlegmatizing fluid is a liquid, this liquid must be a non-solvent for the powdery filler so as not to alter the particle size of said filler; it must also be preferentially non-toxic and non-flammable under the conditions of use.

A titre d'exemple de fluide flegmatisant susceptible d'être mis en oeuvre, on peut citer CO2, N2, l'acétone, l'acétate d'éthyle et les hydrofluoroéthers.As an example of a phlegmatizing fluid that may be used, mention may be made of CO 2 , N 2 , acetone, ethyl acetate and hydrofluoroethers.

Le rapport massique entre fluide flegmatisant et charges pulvérulentes sensibles est généralement de l'ordre de 75/25 à 25/75. Sachant que la pâte de propergol prête à la coulée peut comporter de 65 à 80 % en masse de charges pulvérulentes sensibles, il y a donc en règle générale une quantité très importante de liquide flegmatisant à éliminer.The mass ratio between phlegmatizing fluid and sensitive powdery fillers is generally of the order of 75/25 to 25/75. Knowing that the propellant paste ready for casting may comprise from 65 to 80% by weight of sensitive powdery fillers, there is therefore in general a very large amount of phlegmatizing liquid to eliminate.

Selon l'art antérieur, un tel fluide flegmatisant est généralement éliminé avant que les charges ne soient introduites dans le malaxeur. On voit plus loin que, dans le cadre du procédé de l'invention, les charges flegmatisées peuvent être introduites directement dans le malaxeur, le fluide les flegmatisant étant éliminé dans ledit malaxeur.According to the prior art, such a phlegmatizing fluid is generally removed before the charges are introduced into the mixer. It will be seen later that, in the context of the process of the invention, the phlegmatized charges can be introduced directly into the mixer, the phlegmatizing fluid being eliminated in said mixer.

Dans un tel contexte d'intervention de charges solides pulvérulentes sensibles dans l'élaboration du propergol, donc d'intervention de fluide flegmatisant, on comprend l'intérêt tout particulier du procédé de l'invention qui en optimisant le chauffage de la pâte permet d'optimiser l'élimination in situ du fluide flegmatisant... Ceci est précisé en détail ci-après.In such a context of intervention of pulverulent solid charges sensitive in the development of the propellant, and therefore of phlegmatizing fluid intervention, it is understood the very particular interest of the method of the invention which by optimizing the heating of the pulp makes it possible to optimize the in situ elimination of the phlegmatizing fluid. This is explained in detail below.

Selon une première variante de mise en oeuvre du procédé de l'invention, au moins une fraction de la pâte malaxée est extraite du malaxeur, réchauffée, puis re-introduite dans ledit malaxeur.According to a first alternative embodiment of the process of the invention, at least a fraction of the kneaded paste is extracted from the kneader, reheated, and then re-introduced into said kneader.

On peut ainsi, de manière générale, accélérer la montée en température de la pâte à l'intérieur du malaxeur, l'énergie conférée à la fraction(aux fractions) de pâte réchauffée(s) étant mieux valorisée que si elle avait été communiquée à la masse totale de pâte au sein du malaxeur...Thus, it is generally possible to accelerate the rise in temperature of the dough inside the kneader, the energy conferred to the fraction (fractions) of heated dough (s) being better valued than if it had been communicated to the total mass of dough within the mixer ...

Lorsque le procédé de l'invention comprend l'introduction dans le malaxeur de charges solides pulvérulentes sensibles flegmatisées à l'aide d'au moins un fluide flegmatisant, cette première variante - avec réchauffement - comprend avantageusement la mise en oeuvre du réchauffement (au moins au démarrage du malaxage) dans des conditions de température où ledit au moins un fluide flegmatisant est vaporisé. Ces conditions de température sont bien évidemment à optimiser au vu de la nature du(des) fluide(s) flegmatisant(s) en cause et de l'éventuelle présence de matériaux pyrotechniques. On indique, de façon nullement limitative, que la au moins une fraction de pâte malaxée extraite est alors avantageusement réchauffée à une température comprise entre 50°C et 95°C, très avantageusement à une température comprise entre 55 et 80°C. Dans le cadre de la mise en oeuvre de cette première variante du procédé avec fluide(s) flegmatisant(s), on prévoit avantageusement de récupérer le(s)dit(s) fluide(s) vaporisé(s).When the process of the invention comprises the introduction into the kneader of phlegmatized sensitive solid powdery fillers using at least one phlegmatizing fluid, this first variant - with heating - advantageously comprises the implementation of the heating (at least at the start of mixing) under temperature conditions in which the at least one phlegmatizing fluid is vaporized. These temperature conditions are obviously to be optimized in view of the nature of the phlegmatizing fluid (s) in question and the possible presence of pyrotechnic materials. It is indicated, in no way limiting, that the at least one fraction of milled paste extracted is then advantageously heated to a temperature between 50 ° C and 95 ° C, very advantageously at a temperature between 55 and 80 ° C. In the context of the implementation of this first variant of the process with phlegmatizing fluid (s), it is advantageous to recover the said fluid (s) vaporized (s).

Selon une seconde variante de mise en oeuvre du procédé de l'invention, au moins une fraction de la pâte malaxée est extraite du malaxeur, refroidie, puis réintroduite dans ledit malaxeur.According to a second alternative embodiment of the process of the invention, at least a fraction of the kneaded paste is extracted from the kneader, cooled, and then reintroduced into said kneader.

On peut ainsi, en fin de malaxage, accélérer le refroidissement de la masse totale de pâte à l'intérieur du malaxeur.It is thus possible, at the end of kneading, to accelerate the cooling of the total mass of dough inside the kneader.

On indique, de façon nullement limitative, que la au moins une fraction de pâte malaxée extraite peut ainsi être refroidie à une température comprise entre 55°C et 20°C, plus généralement à une température comprise entre 55°C et 40°C.It is indicated, in no way limiting, that the at least one fraction of milled paste extracted can thus be cooled to a temperature between 55 ° C and 20 ° C, more generally at a temperature between 55 ° C and 40 ° C.

On a déjà précisé que le procédé de l'invention peut être mis en oeuvre dans un premier temps selon la première variante et dans un second temps selon la seconde variante.It has already been stated that the method of the invention can be implemented firstly according to the first variant and in a second step according to the second variant.

A la lecture de ce qui précède, l'homme du métier a déjà saisi tout l'intérêt du procédé de l'invention. En référence aux problèmes techniques invoqués dans l'introduction de la présente description, il permet :

  • de réduire la durée du cycle de malaxage (en assurant notamment un bon malaxage vertical), et donc de diminuer les coûts de fabrication et/ou d'investissement ;
  • d'introduire des charges sensibles, sans modification importante du procédé et surtout sans risque complémentaire.
On reading the foregoing, those skilled in the art have already grasped the whole point of the process of the invention. With reference to the technical problems invoked in the introduction of the present description, it allows:
  • to reduce the duration of the mixing cycle (in particular by ensuring good vertical mixing), and thus to reduce manufacturing and / or investment costs;
  • to introduce sensitive charges, without significant modification of the process and especially without additional risk.

Le procédé de l'invention décrit ci-dessus en référence à la préparation de pâte de propergol, de type composite, en général, convient tout particulièrement à la préparation de chargements composites explosifs. A titre d'exemples de chargements de ce type, on peut mentionner ceux décrits dans la demande EP-A-1 333 015.The process of the invention described above with reference to the preparation of propellant paste, of composite type, in general, is particularly suitable for the preparation of explosive composite loadings. By way of examples of such loadings, mention may be made of those described in application EP-A-1 333 015.

Le procédé de l'invention ne pose pas de difficulté particulière, quant à sa mise en oeuvre. Les paramètres à gérer, voire à optimiser sont bien évidemment, pour une boucle de circulation extérieure, le débit de pâte concernée et l'intensité de l'échange thermique à mettre en oeuvre. On peut mentionner ici, de manière incidente, que la(les) fraction(s) de pâte est(sont) avantageusement prélevée(s), extraite(s), en partie basse de la cuve de malaxage, voire au fond de ladite cuve et réintroduite(s) en partie haute de ladite cuve. L'opération de réintroduction est généralement menée au-dessus de la masse de pâte au sein du malaxeur.The method of the invention does not pose any particular difficulty as to its implementation. The parameters to be managed or even optimized are obviously, for an external circulation loop, the flow rate of the pulp concerned and the intensity of the heat exchange to be implemented. It may be mentioned here, incidentally, that the (the) fraction (s) of pulp is (are) advantageously taken (s), extracted (s), the lower part of the mixing tank, or even the bottom of said tank and reintroduced (s) in the upper part of said tank. The reintroduction operation is generally carried out above the dough mass within the mixer.

Selon son deuxième objet, l'invention concerne un dispositif convenant à la mise en oeuvre du procédé décrit ci-dessus. Ledit dispositif est du type de ceux de l'art antérieur, il a été modifié, dans une moindre mesure, pour inclure au moins une boucle de circulation extérieure équipée d'au moins un échangeur thermique.According to its second object, the invention relates to a device suitable for implementing the method described above. Said device is of the type of those of the prior art, it has been modified, to a lesser extent, to include at least one external circulation loop equipped with at least one heat exchanger.

Plus précisément, le dispositif de l'invention adapté à la préparation d'une pâte de propergol à base d'un liant renfermant des charges solides pulvérulentes (pâte de propergol de type composite) comprend un malaxeur incluant une cuve de malaxage et des moyens de malaxage, des moyens de thermorégulation et de dépressurisation de ladite cuve et des moyens d'introduction des ingrédients constitutifs de la pâte, y compris des moyens d'introduction de charges solides pulvérulentes. En cela, ledit dispositif est du type de ceux de l'art antérieur. De façon caractéristique, il comprend en sus au moins une boucle de circulation extérieure équipée de moyens de circulation et d'au moins un échangeur thermique. Chaque boucle avec ses équipements doit permettre la circulation avec échange thermique d'une fraction de la pâte malaxée.More specifically, the device of the invention adapted to the preparation of a propellant paste based on a binder containing powdery solid charges (composite propellant paste) comprises a kneader including a kneading tank and means of mixing, means of thermoregulation and depressurization of said vessel and means for introducing the constituent ingredients of the dough, including means for introducing powdery solid charges. In this, said device is of the type of those of the prior art. Characteristically, it comprises in addition at least one external circulation loop equipped with circulation means and at least one heat exchanger. Each loop with its equipment must allow circulation with heat exchange of a fraction of the kneaded dough.

Les moyens équipant chacune des boucles de circulation extérieure (équipant la boucle de circulation extérieure) sont évidemment adaptés à la nature de la pâte en cause.The means equipping each of the outer circulation loops (equipping the outer circulation loop) are obviously adapted to the nature of the dough in question.

Les moyens de circulation du type pompe sont plus particulièrement adaptés à la viscosité de ladite pâte.The circulation means of the pump type are more particularly adapted to the viscosity of said paste.

Selon une variante avantageuse, lesdits moyens comprennent une pompe péristaltique.According to an advantageous variant, said means comprise a peristaltic pump.

Selon une autre variante avantageuse, le au moins un échangeur thermique est un mélangeur statique, du type à double enveloppe à circulation forcée de fluide caloporteur à contre-courant. Un tel mélangeur statique assure non seulement le chauffage ou le refroidissement de la pâte de propergol en circulation mais permet également d'améliorer l'homogénéisation de ladite pâte avant sa réintroduction dans la cuve du malaxeur. Ceci contribue à la bonne qualité du produit fini.According to another advantageous variant, the at least one heat exchanger is a static mixer of the jacketed type with forced circulation of heat transfer fluid against the current. Such a static mixer not only ensures the heating or cooling of the circulating propellant paste, but also makes it possible to improve the homogenization of said paste before it is reintroduced into the mixer tank. This contributes to the good quality of the finished product.

Pour ce qui concerne les moyens d'introduction de charges solides pulvérulentes dans la cuve de malaxage, ils peuvent être agencés sur la cuve, indépendamment de toute boucle de circulation extérieure. Ils sont avantageusement agencés pour déboucher dans une(la) boucle de circulation extérieure, très avantageusement agencés, dans un tel cas de figure, en aval du(des) échangeur(s) thermique(s).As regards the means for introducing powdery solid charges into the mixing tank, they can be arranged on the tank, independently of any external circulation loop. They are advantageously arranged to open into an external circulation loop, very advantageously arranged, in such a case, downstream of the heat exchanger (s).

Les moyens de thermorégulation et dépressurisation permettent de contrôler les conditions de température et pression au sein du malaxeur. Les moyens de dépressurisation assurent généralement le vide, au sein dudit malaxeur. Ils interviennent en fait de la même façon qu'ils le font dans les dispositifs de l'art antérieur mais sont en sus susceptibles de contribuer à l'élimination du fluide flegmatisant introduit dans le malaxeur (selon l'art antérieur, ledit fluide était éliminé hors du malaxeur). Auxdits moyens de dépressurisation est avantageusement couplée une unité de condensation. Une telle unité intervient pour la récupération des fluides flegmatisés vaporisés, éventuellement introduits avec les charges solides pulvérulentes.The means of thermoregulation and depressurization make it possible to control the conditions of temperature and pressure within the kneader. The depressurization means generally provide vacuum, within said mixer. They intervene in fact in the same way as they do in the devices of the prior art but are in addition capable of contributing to the elimination of the phlegmatizing fluid introduced into the mixer (according to the prior art, said fluid was eliminated off the mixer). Said depressurization means is advantageously coupled to a condensing unit. Such a unit intervenes for the recovery of vaporized phlegmatized fluids, possibly introduced with the pulverulent solid charges.

La(les) boucle(s) de circulation extérieure est(sont) avantageusement agencée(s) pour assurer une circulation à partir d'une partie basse de la cuve, voire du fond de ladite cuve, vers le haut de ladite cuve. On a vu que la(les)dite(s) boucle(s) débouche(nt) généralement en partie haute, au-dessus du niveau de remplissage prévu pour ladite cuve.The outer loop (s) is (are) advantageously arranged (s) to ensure a flow from a lower part of the tank, or even the bottom of said tank, to the top of said tank. We have seen that (the) said (s) loop (s) leads (nt) generally in the upper part, above the filling level provided for said vessel.

On se propose maintenant d'illustrer l'invention, de manière nullement limitative, par les figures annexées et exemples ci-après.It is now proposed to illustrate the invention, in no way limiting, by the accompanying figures and examples below.

La figure 1 représente schématiquement une variante de réalisation d'un dispositif de l'invention.Figure 1 shows schematically an alternative embodiment of a device of the invention.

La figure 2 représente la vitesse de refroidissement d'une pâte de propergol inerte préparée selon le procédé de l'invention.FIG. 2 represents the cooling rate of an inert propellant paste prepared according to the method of the invention.

Ladite figure 2 est à considérer avec les exemples comparatifs 1a et 1b ainsi que les exemples 2a et 2b de l'invention, donnés ci-après.Said FIG. 2 is to be considered with Comparative Examples 1a and 1b as well as Examples 2a and 2b of the invention, given below.

Sur la figure 1, on a représenté en 1 un malaxeur du type à double enveloppe, dans laquelle circule un fluide caloporteur que l'on peut chauffer ou refroidir à volonté, tel que de l'eau glycolée ;
en 10, la cuve dudit malaxeur 1;
en 12 et 12bis, des moyens de malaxage, plus précisément des pales verticales, solidaires du couvercle du malaxeur 1 et entraînées par un moteur 11 ;
en 14, des moyens de thermorégulation aptes à contrôler la température de la cuve 10 ;
en 16, des moyens de dépressurisation aptes à contrôler la pression (vide ou faible pression) de ladite cuve 10. Auxdits moyens de dépressurisation 16, on a couplé une unité de condensation 17 apte à permettre la récupération d'un fluide flegmatisant, dans l'hypothèse où un tel fluide flegmatisant intervient.In Figure 1, there is shown in 1 a jacketed type of mixer in which circulates a heat transfer fluid that can be heated or cool at will, such as glycol water;
at 10, the vessel of said mixer 1;
at 12 and 12a, kneading means, more precisely vertical blades, secured to the cover of the kneader 1 and driven by a motor 11;
at 14, thermoregulation means able to control the temperature of the tank 10;
at 16, depressurization means able to control the pressure (vacuum or low pressure) of said tank 10. To said depressurization means 16, a condensation unit 17 is coupled capable of allowing the recovery of a phlegmatizing fluid, in the hypothesis where such a phlegmatizing fluid intervenes.

De façon caractéristique, à la cuve 10 du malaxeur 1 est associée une boucle de circulation extérieure 20 équipée de moyens de circulation, une pompe 22, et d'un échangeur thermique 30. La température du fluide caloporteur, circulant dans ledit échangeur thermique 30, est régulée par l'intermédiaire du groupe thermique 32.Characteristically, the tank 10 of the kneader 1 is associated with an external circulation loop 20 equipped with circulation means, a pump 22, and a heat exchanger 30. The temperature of the coolant circulating in said heat exchanger 30, is regulated via the thermal group 32.

La boucle de circulation extérieure 20 présente en son embouchure de réintroduction un tube 24 équipé d'une grille 26. Une telle grille 26 intervient avantageusement pour éviter l'entrée de corps étrangers et favoriser le dégazage de la pâte réintroduite, en partageant le flux de ladite pâte en minces filets.The outer circulation loop 20 has at its reintroduction mouth a tube 24 equipped with a grid 26. Such a grid 26 is advantageously used to prevent the entry of foreign bodies and to promote the degassing of the reintroduced paste, by sharing the flow of said dough in thin threads.

En 18, on a représenté une trémie pour l'introduction de charges solides pulvérulentes. Ladite trémie 18, selon la variante représentée, débouche dans la boucle de circulation 20, en aval de l'échangeur thermique 30.At 18, there is shown a hopper for the introduction of powdery solid charges. Said hopper 18, according to the variant shown, opens into the circulation loop 20, downstream of the heat exchanger 30.

En référence à cette figure 1, on peut rapidement décrire une mise en oeuvre du procédé de l'invention.With reference to this Figure 1, we can quickly describe an implementation of the method of the invention.

De façon classique, on introduit préalablement dans la cuve 10 du malaxeur 1 ouvert, le liant liquide, les charges réductrices (par exemple de la poudre d'aluminium), les différents additifs sauf le réticulant et le catalyseur de réticulation, et les charges oxydantes, par exemple le perchlorate d'ammonium.Conventionally, the open mixer 1, the liquid binder, the reducing charges (for example aluminum powder), the various additives except the crosslinking agent and the crosslinking catalyst, and the oxidizing charges are introduced beforehand into the tank 10. for example ammonium perchlorate.

Le malaxeur 1 est fermé et les ingrédients sont mélangés et chauffés jusqu'à environ 70°C (à cette fin, le fluide caloporteur de la cuve est porté à environ 80°C) ; la mise sous vide (ou faible pression) permet de dégazer le mélange. En continuant à malaxer et à chauffer, on introduit la charge oxydante pulvérulente via la trémie 18 : le chauffage permet de compenser l'augmentation de viscosité due à l'introduction des charges pulvérulentes. On poursuit alors le malaxage et l'homogénéisation de la pâte (on vise généralement à porter ladite pâte homogénéisée à une température entre 20°C et 80°C, préférentiellement entre 50°C et 65°C). Ladite pâte est ensuite refroidie (à cette fin, le fluide caloporteur de la cuve est porté à environ 30°C), jusqu'à la température de coulée, environ 50°C. On introduit alors, toujours par la trémie 18, le réticulant et le catalyseur de réticulation, avant de procéder à la coulée après une dernière séquence d'homogénéisation.The kneader 1 is closed and the ingredients are mixed and heated to about 70 ° C (for this purpose, the coolant of the tank is heated to about 80 ° C); vacuuming (or low pressure) allows the mixture to be degassed. Continuing to knead and heat, the powdery oxidizing charge is introduced via the hopper 18: the heating makes it possible to compensate for the increase in viscosity due to the introduction of the pulverulent fillers. The kneading and homogenization of the dough is then continued (it is generally intended to bring said homogenized dough to a temperature between 20 ° C. and 80 ° C., preferably between 50 ° C. and 65 ° C.). Said paste is then cooled (for this purpose, the coolant of the tank is heated to about 30 ° C), to the casting temperature, about 50 ° C. The crosslinking agent and the crosslinking catalyst are then introduced, still through the hopper 18, before casting after a last homogenization sequence.

La température de la cuve 10 du malaxeur 1 est contrôlée par les moyens 14 ; la pression par le système de dépressurisation 16.The temperature of the tank 10 of the kneader 1 is controlled by the means 14; the pressure by the depressurization system 16.

Selon l'invention, on améliore au moins l'une des étapes de chauffage et refroidissement ci-dessus, en extrayant un flux de pâte du fond de la cuve 1, en le faisant circuler dans la boucle 20 avec réchauffage ou refroidissement (efficace) au niveau de l'échangeur thermique 30 et en le réintroduisant, réchauffé ou refroidi, dans la partie supérieure de la cuve 1 (au-dessus du niveau de la surface de masse de pâte).According to the invention, at least one of the above heating and cooling steps is improved by extracting a flow of dough from the bottom of the vessel 1, circulating it in the loop 20 with heating or cooling (effective) at the heat exchanger 30 and reintroducing it, warmed or cooled, in the upper part of the tank 1 (above the level of the dough body surface).

Le réchauffage en cause peut être un simple réchauffage ou contribuer également à extraire efficacement un fluide flegmatisant introduit avec des charges solides pulvérulentes sensibles flegmatisées.The reheating in question may be a simple reheating or may also help to effectively extract a phlegmatizing fluid introduced with phlegmatized sensitive powdery solid charges.

ExemplesExamples Obtention d'un propergol inerte pour expériences de refroidissementObtaining an inert propellant for cooling experiments

Dans un malaxeur vertical en acier inoxydable de capacité 5 gallons (environ 19 litres), on prépare une pâte de propergol inerte, mais représentative d'un propergol réel (pour s'affranchir des mesures de sécurité), par mélange à environ 65°C-70°C, durant 2 à 3 heures, des ingrédients suivants :

  • 12 % en masse de liant à partir d'un polybutadiène à terminaison hydroxytéléchélique (R45HT d'ATOFINA),
  • 68 % en masse d'une charge pulvérulente inerte (chlorure de potassium) ; et
  • 20 % en masse de poudre d'aluminium.
In a vertical stainless steel kneader with a capacity of 5 gallons (approximately 19 liters), an inert propellant paste, representative of a real propellant (to overcome the safety measures), is prepared by mixing at approximately 65 ° C. -70 ° C, during 2 to 3 hours, of the following ingredients:
  • 12% by weight of binder from a hydroxytelechelic terminated polybutadiene (R45HT from ATOFINA),
  • 68% by weight of an inert powder filler (potassium chloride); and
  • 20% by weight of aluminum powder.

Exemples comparatifs 1a et 1b : refroidissement selon un procédé conventionnelComparative Examples 1a and 1b: Cooling according to a conventional method

La pâte de propergol inerte obtenue ci-dessus est refroidie dans le malaxeur par circulation de fluide caloporteur à 40°C dans la double enveloppe de la cuve du malaxeur. La cuve est sous vide (environ 5 mm Hg), et la vitesse de rotation des pales est de 5 tr/min. On mesure la température de la pâte en fond de cuve pendant l'étape de refroidissement. Pour deux malaxées distinctes, les résultats sont consignés dans le Tableau 1 et représentés sur la figure 2. Tableau 1 T pâte initiale T fluide caloporteur V refroidissement Ex. Comp. 1a 64°C 40°C 0,75°C/min Ex. Comp. 1b 70°C 40°C 0,9°C/min The inert propellant paste obtained above is cooled in the mixer by circulation of coolant at 40 ° C in the jacket of the tank of the kneader. The tank is under vacuum (about 5 mm Hg), and the speed of rotation of the blades is 5 rpm. The temperature of the dough at the bottom of the tank is measured during the cooling step. For two separate kneaded kneads, the results are shown in Table 1 and shown in Figure 2. <u> Table 1 </ u> T initial dough T heat transfer fluid V cooling Ex. Comp. 1a 64 ° C 40 ° C 0.75 ° C / min Ex. Comp. 1b 70 ° C 40 ° C 0.9 ° C / min

Comme on peut le voir sur la figure 2, le refroidissement de la pâte de propergol, de 64°C à 55°C, s'effectue en 12 min (Ex. Comp. 1a), et le refroidissement de 70°C à 55°C s'effectue en 13 à 14 min (Ex. Comp. 1b).As can be seen in FIG. 2, the cooling of the propellant paste, from 64 ° C. to 55 ° C., takes place over 12 minutes (eg Comp. and the cooling from 70 ° C. to 55 ° C. is carried out in 13 to 14 minutes (eg Comp 1b).

Exemples 2a et 2b de l'inventionExamples 2a and 2b of the invention

La même pâte de propergol que celle préparée ci-dessus est refroidie selon le procédé de l'invention. Les conditions de fonctionnement du malaxeur sont identiques à celles des deux exemples comparatifs précédents. Mais, pour la phase de refroidissement, la pâte de propergol est prélevée en fond de cuve par l'intermédiaire d'une pompe péristaltique, passe dans un échangeur thermique puis est réinjectée dans la cuve du malaxeur selon le schéma représenté par la figure 1 ; pour ces essais, le dispositif comporte un seul circuit extérieur.The same propellant paste as that prepared above is cooled according to the method of the invention. The operating conditions of the kneader are identical to those of the two preceding comparative examples. But, for the cooling phase, the propellant paste is taken at the bottom of the tank via a peristaltic pump, passes into a heat exchanger and is reinjected into the mixer tank according to the diagram shown in Figure 1; for these tests, the device comprises a single external circuit.

La pompe péristaltique est une pompe de marque ABAQUE type ALO, dont le débit varie entre 250 kg/h et 150 kg/h suivant la viscosité, croissante, de la pâte lorsque celle-ci se refroidit et que sa température diminue d'environ 70°C à environ 45°C.The peristaltic pump is a pump type ABAQUE ALO type, whose flow varies between 250 kg / h and 150 kg / h depending on the increasing viscosity of the dough when it cools and its temperature decreases about 70 ° C at about 45 ° C.

L'échangeur thermique est constitué par un mélangeur statique de marque SULZER de type SMXL de 30 mm de diamètre et de 800 mm de longueur ; il comporte une double paroi avec circulation d'un fluide caloporteur à 30° C pour l'exemple 2a et à 20°C pour l'exemple 2b.The heat exchanger consists of a SULZER static mixer type SMXL 30 mm in diameter and 800 mm in length; it comprises a double wall with circulation of a heat transfer fluid at 30 ° C for Example 2a and at 20 ° C for Example 2b.

On mesure la température de la pâte de propergol en fond de cuve pendant l'étape de refroidissement. Pour deux malaxées distinctes, les résultats sont consignés dans le Tableau 2 et représentés sur la figure 2. Tableau 2 T pâte initiale T fluide caloporteur échangeur V refroidissement Ex. 2a 66°C 30°C 1,75°C/min Ex. 2b 69°C 20°C 3°C/min The temperature of the propellant paste is measured at the bottom of the tank during the cooling step. For two separate kneaded kneads, the results are shown in Table 2 and shown in Figure 2. <u> Table 2 </ u> T initial dough Heat transfer fluid exchanger V cooling Ex. 2a 66 ° C 30 ° C 1.75 ° C / min Ex. 2b 69 ° C 20 ° C 3 ° C / min

Comme on peut le voir sur la figure 2, la mise en oeuvre du procédé de l'invention permet de refroidir la pâte de propergol de 66°C à 55°C en environ 6 min. (Ex. 2a), et de 69°C à 55°C en 5 min (Ex. 2b). La vitesse de refroidissement est donc doublée (Ex. 2a v. Ex. Comp. 1a), voire triplée (Ex. 2b v. Ex. Comp. 1b).As can be seen in Figure 2, the implementation of the method of the invention allows to cool the propellant paste from 66 ° C to 55 ° C in about 6 min. (Ex 2a), and 69 ° C to 55 ° C in 5 min (Ex 2b). The The cooling rate is thus doubled (eg 2a v. Ex .: Comp 1a) or tripled (eg 2b v. Ex Comp 1b).

Exemple 3 : élimination de fluide flegmatisantExample 3: elimination of phlegmatizing fluid

On flegmatise une charge sensible (hexogène) en mélangeant 1,5 kg de ladite charge sensible à 4,5 kg d'un hydrofluoroéther liquide, commercialisé sous la dénomination HFE 7100 par la Société 3M. La température d'ébullition du HFE 7100 est de 61°C à la pression atmosphérique ; de plus, ce produit n'est ni cancérigène, ni mutagène, et il n'est pas nocif pour la reproduction (non CMR). Enfin il est ininflammable dans les présentes conditions d'utilisation.A sensitive charge (hexogen) is phlegmatized by mixing 1.5 kg of said sensitive charge with 4.5 kg of a liquid hydrofluoroether, marketed under the name HFE 7100 by the company 3M. The boiling point of HFE 7100 is 61 ° C at atmospheric pressure; moreover, this product is neither carcinogenic nor mutagenic and is not harmful for reproduction (non-CMR). Finally it is not flammable in these conditions of use.

Dans la cuve d'un petit malaxeur vertical de 1 gallon (3,8 litres), qui contient déjà 1,5 kg de liant liquide, on introduit par gravité les 6 kg de mélange flegmatisé par une trémie. L'eau de la double enveloppe de la cuve est maintenue à 65°C. Par la boucle extérieure on prélève environ 10 kg/h du mélange et on les fait transiter dans un échangeur SULZER SMXL de diamètre 36 mm et de longueur 240 mm dont la double enveloppe est aussi chauffée à 65°C ; l'hydrofluoroéther (HFE) est vaporisé et les vapeurs sont reprises dans le malaxeur, puis évacuées vers le piège lorsque la pâte est réinjectée dans le malaxeur. Au bout de 25 minutes, on constate que :

  • le condenseur ne débite plus : donc il n'y a plus de vapeur de HFE ;
  • la puissance demandée par le moteur du malaxeur augmente : la pâte devient plus visqueuse car le HFE liquide est éliminé.
In the tank of a small 1 gallon (3.8 liter) vertical mixer, which already contains 1.5 kg of liquid binder, the 6 kg of phlegmatized mixture is gravity fed through a hopper. The water of the double jacket of the tank is maintained at 65 ° C. By the outer loop is taken about 10 kg / h of the mixture and passed through a SULZER SMXL exchanger of diameter 36 mm and length 240 mm, the double jacket is also heated to 65 ° C; the hydrofluoroether (HFE) is vaporized and the vapors are taken up in the mixer, then discharged to the trap when the paste is reinjected into the mixer. After 25 minutes, we find that:
  • the condenser no longer delivers: so there is no more HFE vapor;
  • the power demanded by the motor of the mixer increases: the paste becomes more viscous because the liquid HFE is eliminated.

L'élimination du liquide flegmatisant est donc rapide en utilisant le procédé de l'invention. A titre indicatif, on estime que l'élimination de la même quantité de HFE en utilisant un procédé de malaxage classique, c'est-à-dire sans circulation de la pâte de propergol dans une boucle extérieure, nécessiterait entre 1h et 2h.The removal of the phlegmatizing liquid is therefore rapid using the method of the invention. As an indication, it is estimated that the removal of the same amount of HFE using a conventional mixing process, that is to say without circulation of the propellant paste in an outer loop, would require between 1h and 2h.

Claims (13)

Procédé de préparation d'une pâte de propergol à base d'un liant renfermant des charges solides pulvérulentes, ledit procédé comprenant successivement l'introduction dans un malaxeur (1) des ingrédients constitutifs de ladite pâte puis le malaxage, dans ledit malaxeur (1), dans des conditions de température et pression adéquates, de la pâte constituée, caractérisé en ce qu'en cours dudit malaxage : - au moins une fraction de la pâte malaxée est extraite dudit malaxeur (1) ; - ladite au moins une fraction de la pâte malaxée extraite est soumise à un échange thermique ; et - ladite au moins une fraction de pâte malaxée extraite, réchauffée ou refroidie, est réintroduite dans ledit malaxeur (1). Process for the preparation of a propellant paste based on a binder containing solid powdery fillers, said process comprising successively the introduction into a kneader (1) of the constituent ingredients of said dough and then kneading, in said kneader (1) , under suitable temperature and pressure conditions, the paste formed, characterized in that during said kneading: at least a fraction of the kneaded pulp is extracted from said kneader (1); said at least one fraction of the extracted kneaded pulp is subjected to a heat exchange; and said at least one fraction of kneaded pulp extracted, heated or cooled, is reintroduced into said kneader (1). Procédé selon la revendication 1, caractérisé en ce qu'il comprend l'introduction dans ledit malaxeur de charges solides pulvérulentes pas ou peu sensibles et/ou de charges solides pulvérulentes sensibles flegmatisées à l'aide d'au moins un fluide flegmatisant.Process according to claim 1, characterized in that it comprises the introduction into said kneader of powdery solid charges which are not or only slightly sensitive and / or of pulverulent sensitive solid charges which are phlegmatized with at least one phlegmatizing fluid. Procédé selon l'une des revendications 1 ou 2, caractérisé en ce que ladite au moins une fraction de pâte malaxée extraite est réchauffée.Method according to one of claims 1 or 2, characterized in that said at least one fraction of kneaded paste extracted is heated. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'il comprend l'introduction dans ledit malaxeur de charges solides pulvérulentes sensibles flegmatisées à l'aide d'au moins un fluide flegmatisant et le réchauffage de ladite au moins une fraction de pâte malaxée extraite dans des conditions de température où ledit au moins un fluide flegmatisant est vaporisé.Process according to any one of claims 1 to 3, characterized in that it comprises the introduction into said mixer of phlegmatized sensitive solid powdery solid charges using at least one phlegmatizing fluid and heating said at least one fraction of kneaded pulp extracted under temperature conditions in which the at least one phlegmatizing fluid is vaporized. Procédé selon la revendication 4, caractérisé en ce que ladite au moins une fraction de pâte malaxée extraite est réchauffée à une température comprise entre 50°C et 95°C, avantageusement entre 55°C et 80°C.Process according to Claim 4, characterized in that the said at least one extracted kneaded pulp fraction is heated to a temperature of between 50 ° C and 95 ° C, advantageously between 55 ° C and 80 ° C. Procédé selon l'une des revendications 4 ou 5, caractérisé en ce que ledit au moins un fluide flegmatisant vaporisé est récupéré.Process according to one of Claims 4 or 5, characterized in that the said at least one vaporized phlegmatizing fluid is recovered. Procédé selon l'une des revendications 1 ou 2, caractérisé en ce que ladite au moins une fraction de pâte malaxée extraite est refroidie.Process according to one of Claims 1 or 2, characterized in that the said at least one fraction of milled pulp extracted is cooled. Procédé selon la revendication 7, caractérisé en ce que ladite au moins une fraction de pâte malaxée extraite est refroidie à une température comprise entre 55°C et 20°C, plus généralement comprise entre 55°C et 40°C.Process according to Claim 7, characterized in that the said at least one extracted kneaded paste fraction is cooled to a temperature between 55 ° C and 20 ° C, more generally between 55 ° C and 40 ° C. Dispositif convenant à la préparation d'une pâte de propergol à base d'un liant renfermant des charges solides pulvérulentes, comprenant un malaxeur (1) incluant une cuve de malaxage (10) et des moyens de malaxage (12, 12bis) ainsi que des moyens de thermorégulation (14) et de dépressurisation (16) de ladite cuve (10) et des moyens d'introduction des ingrédients constitutifs de ladite pâte, y compris des moyens d'introduction (18) de charges solides pulvérulentes, caractérisé en ce qu'il comprend en outre au moins une boucle de circulation extérieure (20) équipée de moyens de circulation (22) et d'au moins un échangeur thermique (30), destinée à la circulation avec échange thermique d'une fraction de la pâte de propergol malaxée dans ladite cuve (1).Device suitable for the preparation of a propellant paste based on a binder containing powdery solid charges, comprising a kneader (1) including a kneading bowl (10) and kneading means (12, 12a) and means for thermoregulation (14) and depressurization (16) of said tank (10) and means for introducing the constituent ingredients of said dough, including means (18) for introducing powdery solid charges, characterized in that it further comprises at least one external circulation loop (20) equipped with movement means (22) and at least one heat exchanger (30) for circulating heat exchange with a fraction of the pulp propellant kneaded in said tank (1). Dispositif selon la revendication 9, caractérisé en ce que lesdits moyens de circulation (22) comprennent une pompe péristaltique.Device according to claim 9, characterized in that said circulation means (22) comprise a peristaltic pump. Dispositif selon la revendication 9 ou 10, caractérisé en ce que ledit au moins un échangeur thermique (30) est un mélangeur statique, du type à double enveloppe à circulation forcée de fluide caloporteur à contre-courant.Device according to claim 9 or 10, characterized in that said at least one heat exchanger (30) is a static mixer of the double-jacketed type with forced circulation of heat transfer fluid against the current. Dispositif selon l'une quelconque des revendications 9 à 11, caractérisé en ce que lesdits moyens d'introduction (18) de charges solides pulvérulentes débouchent dans ladite au moins une boucle de circulation extérieure (20), avantageusement en aval du(des) échangeur(s) thermique(s) (30).Device according to any one of claims 9 to 11, characterized in that said means (18) for introducing powdery solid charges open into said at least one external circulation loop (20), advantageously downstream of the exchanger (s) (s) thermal (s) (30). Dispositif selon l'une quelconque des revendications 9 à 12, caractérisé en ce qu'une unité de condensation (17) est couplée aux moyens de dépressurisation (16).Device according to one of Claims 9 to 12, characterized in that a condensation unit (17) is coupled to the depressurization means (16).
EP05292264A 2004-11-02 2005-10-26 Process and apparatus for the preparation of a composite-type solid propellant paste Withdrawn EP1652574A3 (en)

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FR0411638A FR2877333B1 (en) 2004-11-02 2004-11-02 PROCESS AND DEVICE FOR PREPARING A COMPOSITE-TYPE PROPERGOL PASTE

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