Method for extracting ammonium perchlorate from solid composite propellants

Abstract

The present invention relates to a method for recovering ammonium perchlorate from a solid composite propellant, wherein the method is carried out at a temperature of less than 50°C, including the immersion of a solid composite propellant fragment in the form of an aqueous suspension, and the method is terminated when the ionic conductivity in the aqueous suspension reaches a stabilized value of less than 60 mS / cm.

Description

Technology Field

[0001] The present invention relates to the field of treatment and inactivation of solid composite propellants.

[0002] In fact, the present invention aims to provide a simple, easy-to-implement, and environmentally friendly method that allows for the total extraction of ammonium perchlorate from a composite propellant. Background Technology

[0003] A solid composite propellant is an energy composition consisting of a macromolecular matrix of a combustible polymer, referred to as a binder, loaded with an oxidizing agent and a reducing agent. Generally, these oxidizing agent and reducing agent are in the form of a solid powder and a powder metal, respectively.

[0004] Solid composite propellants are widely used in astronautics, either in the takeoff assist boosters of space launchers or in the retrorockets of space probes. They are also used in "airbag" type devices for automotive safety.

[0005] The dismantling of thrusters or retro-rockets using solid composite propellants in equipment return is a problem that has been studied for years. In fact, the return of thrusters and retro-rockets leads to the problem of their destruction. This applies equally to manufacturing waste of solid composite propellants.

[0006] The first destruction method used for reaction propulsion engines and retro-rockets is to mount them on a test stand to be launched and allow them to be destroyed. This process causes atmospheric pollution, particularly during the launch of the first and second stages of the reaction propulsion engine, given that a large amount of solid composite propellant is burned.

[0007] The second method commonly used for the disposal of solid composite propellant manufacturing waste is open burning. Combustion by open burning is limited by weather conditions and generates combustion products that are air pollutants.

[0008] To date, the destruction of reaction propulsion engines by combustion has been permitted. Environmental restrictions have not justified investment and research funding for more environmentally friendly destruction projects.

[0009] However, other more environmentally friendly methods have been developed, some of which involve the underwater milling of solid composite propellant-based waste. Accordingly, patent application FR 2 931 814 provides a process for purifying aqueous solutions containing ammonium perchlorate and possibly nitrates obtained as a result of such milling before disposal. In processes used to date, the underwater milling of solid composite propellant-based waste has not allowed for the extraction of all ammonium perchlorate. The problem to be solved

[0010] Accordingly, the inventors have set the goal of providing a process that is easy to implement and enables the extraction of all ammonium perchlorate initially contained in solid composite propellant-based waste, thereby enabling the externalization of inert solid composite propellant waste from conventional incineration routes to flue gas treatment. means of solving the problem

[0011] To this end, the present invention provides a method for recovering ammonium perchlorate contained in a solid composite propellant, said method

[0012] i) a step of contacting the solid composite propellant in the form of pieces with a first aqueous solution;

[0013] ii) a step of fragmenting the piece of solid composite propellant present in the first aqueous solution to obtain a piece of solid composite propellant having a maximum dimension not exceeding 10 mm;

[0014] iii) a step of obtaining an aqueous solution by adding a second aqueous solution to the mixture obtained in step ii), wherein the amount of water has a mass ratio W / P of 2.5 to 6.8, and stirring the entire mixture, wherein W represents the sum of the mass of water in the first aqueous solution and the mass of water in the second aqueous solution, and P represents the mass of the solid composite propellant existing in the form of pieces;

[0015] iv) a step of maintaining the stirring for a time sufficient for the ammonium perchlorate to be solubilized in the continuous phase of the suspension, wherein the solubilization is monitored by measuring the ionic conductivity of the aqueous suspension;

[0016] v) When the ionic conductivity reaches a stabilized value of less than 60 mS / cm, the step of separating the dispersed phase and the continuous phase of the aqueous suspension is included;

[0017] Steps (i) to (iv) of the above method are performed at the same or different temperatures of 50°C or lower.

[0018] The method according to the present invention has at least one of the following optional characteristics taken alone or in combination.

[0019] The maximum dimensions of the piece of solid composite propellant implemented in step i) do not exceed 50 mm.

[0020] The dimensions of the piece of solid composite propellant implemented in step i) are less than or equal to the dimensions of a rectangular prism of 25 mm x 25 mm x 50 mm.

[0021] The W / P mass ratio is 4.

[0022] In step iv) above, if the ionic conductivity of the aqueous suspension has a stabilized value of 60 mS / cm or higher, a portion of the continuous phase of the suspension is replaced with a third aqueous solution.

[0023] Steps (i) to (iv) of the above method are performed at the same or different temperatures of 30°C to 40°C.

[0024] The first aqueous solution, the second aqueous solution and / or the third aqueous solution contains an anti-stick agent.

[0025] The first aqueous solution consists of water and an anti-stick agent, the second aqueous solution consists of water, and / or the third aqueous solution consists of water.

[0026] The anti-stick agent is selected from the group consisting of talc, glycerol monostearate, kaolin, calcium carbonate, magnesium trisilicate, stearic acid, calcium stearate, magnesium stearate, zinc stearate, glycerol monostearate, glycerol palmitostearate, polyethylene glycol, benenic acid glycerol ester, colloidal silicon dioxide, fine silicon dioxide, aluminum hydroxide, hydrogenated vegetable oil, anionic surfactants, nonionic surfactants, and amphoteric surfactants. Brief explanation of the drawing

[0027] FIG. 1 is a schematic diagram of a method for recovering ammonium perchlorate from a solid composite propellant according to the present invention. FIG. 2 is a schematic diagram of the flow of a complete solid composite propellant processing line in which the "maceration extraction" block corresponds to the ammonium perchlorate recovery method according to the present invention. Specific details for implementing the invention

[0028] The present invention provides a method for processing a solid composite propellant that enables the extraction and recovery of at least 95 mass%, at least 97 mass%, at least 98 mass%, at least 99 mass%, at least 99.5 mass%, ideally all of the contained ammonium perchlorate (NH4ClO4).

[0029] In fact, the inventors have indicated that it is possible to ensure the total extraction of ammonium perchlorate initially contained in the solid composite propellant from a reasonable combination of parameters implemented during the step of extracting ammonium perchlorate from the solid composite propellant, namely, the size of the pieces and fragments of the solid composite propellant introduced into the method, the mass ratio between water and propellant, and the extraction temperature.

[0030] First, the method for recovering ammonium perchlorate from a solid composite propellant according to the present invention is included in an environmentally friendly pathway for treating solid composite propellant-based waste. In practice, the present invention allows the solid composite propellant to be inactivated by an ammonium perchlorate extraction method, thereby allowing the inactivated solid composite propellant waste to be externalized into a conventional incineration pathway for flue gas treatment.

[0031] The method for recovering ammonium perchlorate from a solid composite propellant according to the present invention is performed entirely underwater, thereby allowing the propellant to be cut while minimizing risk. Furthermore, the operating conditions implemented within the scope of the method according to the present invention—namely, low heating, simple mechanics, and a high proportion of water—have the advantage of being a simple method with operating conditions having limited risk, and this method is considered non-pyrotechnical after loading the extractant into the reactor. In particular, temperature control during the method according to the present invention makes it possible to minimize the reaction between a reducing agent, such as powdered aluminum contained in the solid composite propellant, and water contained in different aqueous solutions implemented.

[0032] Finally, the method for recovering ammonium perchlorate from a solid composite propellant according to the present invention makes it possible to obtain an aqueous solution containing all of the ammonium perchlorate, as well as a reducing agent-containing polymer residue having an interesting calorific potential for an incineration route in which the extraction residue is processed.

[0033] Accordingly, the present invention relates to a method for recovering ammonium perchlorate contained in a solid composite propellant, and said method

[0034] i) a step of contacting the solid composite propellant in the form of pieces with a first aqueous solution;

[0035] ii) a step of fragmenting the piece of solid composite propellant present in the first aqueous solution to obtain a piece of solid composite propellant having a maximum dimension not exceeding 10 mm;

[0036] iii) a step of obtaining an aqueous suspension by adding a second aqueous solution to the mixture obtained in step ii), wherein the amount of water has a W / P mass ratio of 2.5 to 6.8, and stirring the entire mixture, wherein W represents the sum of the mass of water in the first aqueous solution and the mass of water in the second aqueous solution, and P represents the mass of the solid composite propellant existing in the form of flakes;

[0037] iv) a step of maintaining the stirring for a time sufficient for the ammonium perchlorate to be solubilized in a continuous phase of the suspension, wherein the solubilization is monitored by measuring the ionic conductivity of the aqueous suspension;

[0038] v) When the ionic conductivity reaches a stabilized value of less than 60 mS / cm, the step of separating the dispersed phase and the continuous phase of the aqueous suspension is included;

[0039] Steps (i) to (iv) of the above method are performed at the same or different temperatures of 50°C or lower.

[0040] "Solid composite propellant" within the scope of the present invention means an energy composition comprising a polymer binder, a reducing agent, and an oxidizing agent, wherein the oxidizing agent comprises or consists of ammonium perchlorate.

[0041] The present invention applies to any solid composite propellant in which the oxidizing agent comprises or consists of ammonium perchlorate, regardless of the properties of the polymer binder and the reducing agent.

[0042] Typically, the polymer binder present in the solid composite propellant processed within the scope of the present invention is a polyurethane or polybutadiene, such as, for example, hydroxytelecelic polybutadiene (HTPB), polybutadiene-acrylic acid-acrylonitrile terpolymer (PBAN) or carboxytelecelic polybutadiene (CTPB).

[0043] Typically, the reducing agent present in the solid composite propellant processed within the scope of the present invention is powdered aluminum or powdered magnesium.

[0044] The solid composite propellant processed within the scope of the present invention essentially originates from the solid composite propellant manufacturing unit or the drainage unit of the equipment return reaction propulsion engine. Accordingly, the solid composite propellant is provided in various sizes and shapes. Generally, the maximum size of the solid composite propellant is 80 cm.

[0045] The inventors have indicated that one of the parameters promoting the total extraction of ammonium perchlorate is the size of the solid composite propellant pieces introduced into the method. Accordingly, the maximum dimensions of these pieces do not exceed 50 mm.

[0046] For this purpose, it may be necessary to apply the solid composite propellant to one or more milling steps before implementing the method according to the present invention. Typically, the solid composite propellant is applied to two preliminary milling steps performed by knife mills. These two milling steps make it possible to obtain a piece of composite propellant with the largest dimension being 50 mm or less, in particular, with dimensions of 25 mm x 25 mm x 50 mm or less.

[0047] The solution implemented in step i) of the method according to the present invention comprises water as a solvent, thus describing the designation of an aqueous solution. Within the scope of the present invention, "water" means tap water, deionized water, distilled water, or even ultrapure water (18.2 MΩ). The solution implemented in step i) of the method according to the present invention may be a neutral, acidic, or basic aqueous solution. Typically, the solution implemented in step i) is an aqueous solution having a pH of 4 to 9.

[0048] Typically, the aqueous solution implemented in step i) contains only water, that is, it consists of water. Alternatively, it may contain at least one other element in addition to the solvent, which is water. This other element is, in particular, an anti-stick agent.

[0049] "Anti-sticking agent" means a compound capable of limiting the adhesiveness of the fragments of a solid composite propellant and subsequently its fragments, and thus preventing the fragments of the solid composite propellant and subsequently its fragments from aggregating together and re-aggregating. It should be noted that the temperatures of steps (i) to (iv) below 50°C, particularly between 30°C and 40°C, also make it possible to control the re-aggregation of the fragments or fragments of the solid composite propellant. Any anti-sticking agent known to a person skilled in the art may be used within the scope of the present invention. Advantageously, an anti-stick agent implemented within the scope of the present invention is selected from the group consisting of talc, glycerol monostearate, kaolin, calcium carbonate, magnesium trisilicate, stearic acid, calcium stearate, magnesium stearate, zinc stearate, glycerol monostearate, glycerol palmitostearate, polyethylene glycol, glycerol benenic acid ester, colloidal silicon dioxide, fine silicon dioxide, aluminum hydroxide, hydrogenated vegetable oil, anionic surfactants, nonionic surfactants and amphoteric surfactants.

[0050] For reference, a surfactant is a molecule containing a lipophilic (non-polar) part and a hydrophilic (polar) part.

[0051] Among the latter, anionic surfactants contain ammonium ions (NH4 + It has a negatively charged hydrophilic moiety such as alkyl or aryl sulfonates, sulfates, phosphates, or sulfosuccinates associated with counterions such as quaternary ammoniums like tetrabutylammonium, and alkaline cations like Na+, Li+, and K+. As an anionic surfactant, it is possible to use, for example, tetraethylammonium p-toluenesulfonate, sodium dodecylsulfate, sodium palmitate, sodium stearate, sodium myristate, sodium di(2-ethylhexyl)sulfosuccinate, methylbenzene sulfonate, and ethylbenzene sulfonate.

[0052] The surface-active properties, particularly the hydrophilicity, of nonionic (or neutral) surfactants are provided by uncharged functional groups, such as alcohols, ethers, esters, or amides, containing heteroatoms such as nitrogen or oxygen; due to the low hydrophilic contribution of these functional groups, nonionic surfactant compounds are typically polyfunctional. As nonionic surfactants, it is possible to use polyethers, such as polyethoxylated surfactants, such as polyethylene glycol lauryl ether (POE23 or Brij® 35), polyols (sugar-derived surfactants), particularly glucose alkylates, such as glucose hexanate.

[0053] Amphoteric surfactants are compounds that behave as both acids and bases depending on the medium in which they are placed. As amphoteric surfactants, it is possible to use disodium lauroamphodiacetate, betaine, such as alkylamidopropyl betaine or laurylhydroxysulfo betaine.

[0054] When an anti-stick agent is present in the first aqueous solution implemented in step i), the anti-stick agent is used in an amount of 5 mass% or less with respect to the mass of the propellant being treated, particularly in an amount of 1 mass% to 3 mass% with respect to the mass of the propellant being treated.

[0055] Contact during step i) is performed in a reactor, and the dimensions of the reactor are adapted to the amount of solid composite propellant to be processed.

[0056] Different implementations may be considered for carrying out the step of contacting a piece of solid composite propellant with a first aqueous solution containing additional elements, such as an anti-stick agent, in addition to water, optionally. Thus, in a reactor, it is possible to place the piece of solid composite propellant after the first aqueous solution, or to place the first aqueous solution after the piece of solid composite propellant. In these different cases, and where the first aqueous solution contains additional elements, such as an anti-stick agent, in addition to water, the latter may be placed in the reactor before or after the first aqueous solution or before or after the piece of solid composite propellant, or the latter may be mixed with the first aqueous solution in advance before being introduced into the reactor.

[0057] FIG. 1 illustrates a specific embodiment in which water is introduced into a reactor, and then an anti-sticking agent is added to the water to obtain a first aqueous solution consisting of water and an anti-sticking agent, and then a piece of solid composite propellant is introduced into a reactor filled with the first aqueous solution.

[0058] The duration of step i) is variable and essentially depends on the amount of solid composite propellant pieces introduced into the reactor. Typically, step i) can last from 30 minutes to 2 hours. For example, step i) is particularly 1.5 10 as illustrated in FIG. 1. 3 For a piece of 1 kg of solid composite propellant, it can last for about 1 hour (i.e., 1 hour ± 15 minutes).

[0059] Step i) is carried out at a temperature of 50°C or lower, particularly between 30°C and 40°C. For this purpose, Step i) is carried out in an automatic temperature-controlled reactor.

[0060] Step ii) of the method according to the present invention is the step of fragmenting a piece of solid composite propellant to obtain a piece of solid composite propellant having a smaller size, namely, a piece having a maximum dimension of 10 mm or less, in particular a dimension of 10 mm x 10 mm x 10 mm or less.

[0061] Such fragmentation is achieved by means commonly used in reactors to fragment, disperse, and / or mill elements, such as a dispersion / fragmentation turbine or a rotor-stator system. These means advantageously have a peripheral speed of 10 m / s or more.

[0062] The duration of step ii) is variable and essentially depends on the amount of solid composite propellant fragments to be fragmented in the reactor. Typically, step ii) may last from 15 minutes to 2.5 hours. For example, step ii) is, as illustrated in FIG. 1, particularly 1.5 10 3 It can last for 30 to 90 minutes for kg of solid composite propellant pieces to fragment.

[0063] Step ii) is carried out at a temperature of 50°C or lower, particularly at a temperature of 30°C to 40°C. For this purpose, Step ii) is carried out in a thermostatic reactor. Step ii) is carried out in the same thermostatic reactor as implemented for Step i).

[0064] In step iii), the second aqueous solution is added to the mixture obtained at the end of step ii) in the self-temperature controlled reactor implemented in steps i) and ii). This mixture consists of solid composite propellant fragments dispersed in the first aqueous solution, and it is possible that some of the ammonium perchlorate initially present in the solid composite propellant fragments exists in a form already dissolved in the first aqueous solution.

[0065] The second aqueous solution implemented in step iii) of the method according to the present invention comprises water as a solvent, thus describing the name of the aqueous solution. Typically, the second aqueous solution implemented in step iii) comprises only water, that is, it consists of water. Alternatively, it may comprise at least one other element in addition to the solvent which is water. This other element is, in particular, an anti-sticking agent as previously defined. If an anti-sticking agent is present in the second aqueous solution implemented in step iii), the anti-sticking agent is used in an amount of 5 mass% or less relative to the mass of the propellant being treated, particularly in an amount of 1 mass% to 3 mass% relative to the mass of the propellant being treated. The composition of the second aqueous solution may be the same as or different from the composition of the first aqueous solution.

[0066] FIG. 1 illustrates an embodiment in which the second aqueous solution contains only water, that is, is composed of water.

[0067] As previously described, the inventors' work has shown that one of the parameters affecting the total extraction of ammonium perchlorate initially contained in the pieces of solid composite propellant is the mass ratio between the mass of water contained in the first and second aqueous solutions (designated as "W") and the mass of the solid composite propellant to be processed (designated as "P"). This mass corresponds, in practice, to the mass of the pieces of solid composite propellant implemented in step i) of the method according to the present invention. It is self-evident that the mass of water and the mass of the propellant must be expressed in the same mass units. This W / P mass ratio is 2.5 to 6.8, particularly 3 to 6, particularly 3.5 to 5, and more particularly 4. In practice, the amount of the second aqueous solution implemented in step ii) will depend on the amount of water contained, the amount of water contained in the first aqueous solution, and the target W / P mass ratio.

[0068] During step iii) and after the addition of the second aqueous solution, the entire process is stirred to obtain an aqueous suspension. This aqueous suspension initially comprises a dispersed phase corresponding to a solid composite propellant fragment, and a continuous phase comprising a mixture of the first aqueous solution and the second aqueous solution and optionally a portion of already dissolved ammonium perchlorate.

[0069] Step iii) implemented in the automatic temperature-controlled reactor used in steps i) and ii) is carried out at a temperature of 50°C or lower, particularly between 30°C and 40°C.

[0070] Step iv) of the method according to the present invention is a suitable ammonium perchlorate extraction step. In practice, by maintaining stirring, the fragment of the solid composite propellant is maintained in a suspension state, and the solubilization of perchlorate in the continuous phase of the suspension is promoted. It is evident that the chemical composition of the aqueous suspension changes during step iv), and the solid composite propellant fragment loses the powdered ammonium perchlorate initially contained over time, while at the same time the continuous phase of the aqueous suspension becomes enriched with dissolved ammonium perchlorate.

[0071] Step iv) is carried out in the same automatic temperature-controlled reactor as implemented in steps i) to iii) of the method according to the present invention. Consequently, step iv) is carried out at a temperature of 50°C or lower, particularly at a temperature of 30°C to 40°C.

[0072] Additionally, the automatic temperature-controlled reactor is equipped with means suited for stirring the solid composite propellant fragments and maintaining them in a suspension state. For this purpose, any means known to a person skilled in the art may be used within the scope of the present invention. Typically, the means suited for stirring the solid composite propellant fragments and maintaining them in a suspension state is, in particular, a three-bladed propeller optionally combined with a counter-rotating anchor. The dimensions of the three-bladed propeller are defined by the target fluidization velocity as a function of the characteristics of the solid composite propellant fragments dispersed in the suspension. In turn, the counter-rotating anchor serves to limit the dead zone and reduce vortices, thereby preventing cavitation of the dispersion means.

[0073] The automatic temperature-controlled reactor is also equipped with means adapted to measure the ionic conductivity of the suspension contained in the reactor. Any means for measuring ionic conductivity known to the art may be used within the scope of the present invention. Typically, the automatic temperature-controlled reactor is equipped with a conductivity meter arranged to measure the ionic conductivity of the contained suspension.

[0074] During step iv), measurements of ionic conductivity may be performed in a continuous or punctual manner, where the time interval between two continuous measurements may be regular or irregular.

[0075] The duration of step iv) is variable and essentially depends on the amount of composite propellant fragment. Typically, step iv) may last from 6 to 15 hours. For example, step iv) is 1.5 10, particularly implemented initially as illustrated in FIG. 1. 3For a piece of a kg of solid composite propellant, it can last for less than 10 hours, particularly 8 to 9.5 hours.

[0076] Step v) of the method according to the present invention is a step in which the extraction is allowed to be terminated from the moment the ion conductivity in the suspension reaches a stabilized value of less than 60 mS / cm.

[0077] A stabilized value refers to a value of ionic conductivity measured in a suspension that does not change upward or downward by more than 1 mS / cm for a period of more than 60 seconds. This stabilization phase may be longer or shorter, ranging from 1 hour to 6 hours, depending on the product. Signal stability is studied by an automated device after a period of 1 hour, which cannot be shortened to ensure total extraction on the lightly loaded product.

[0078] Accordingly, during step v) of the method according to the present invention, the dispersed phase and the continuous phase are separated from the aqueous suspension obtained at the end of the extraction.

[0079] In the latter, the dispersed phase essentially comprises a polymer acting as a binder in the solid composite propellant, and this polymer contains a reducing agent of the solid composite propellant such as aluminum or magnesium. Therefore, this residue is no longer a pyrotechnic product. It can be disposed of by conventional routes of incinerating or recovering the reducing agent such as aluminum.

[0080] The continuous phase of the aqueous suspension obtained at the end of the extraction is an aqueous solution containing ammonium perchlorate. This solution, commonly referred to as "brine," may be biologically treated as provided in patent application FR 2 931 814 before being discharged.

[0081] This separation in step v) of the above method is carried out by emptying the reactor in which steps i) through iv) are implemented. Two phases are extracted, and the liquid-solid separation allows the continuous phase to be recovered for biological treatment; and the solid phase to be recovered for an optional dehydration step before being reclaimed by incineration.

[0082] Once ammonium perchlorate is extracted, step v) of the method according to the present invention does not need to be performed at a temperature of 30°C to 40°C. This step v) can be performed at room temperature. "Room temperature" means a temperature of approximately 23°C (i.e., 23°C ± 5°C).

[0083] After separating the dispersed phase from the continuous phase in step v), it is possible to extract as much of the continuous phase as possible by dehydrating the dispersed phase thus recovered. Any dehydration technique known to a person skilled in the art may be used within the scope of the present invention.

[0084] During step iv) of the method according to the present invention, it is possible for the ionic conductivity of the aqueous suspension to have a stabilized value of 60 mS / cm or higher. Such a stabilized value does not mean that the extraction of ammonium perchlorate is complete, but rather that it is necessary to renew the continuous phase of the suspension to ensure the inert nature of the residue at the end of the method and to complete the extraction of ammonium perchlorate still present in the dispersed phase.

[0085] Accordingly, under these conditions, namely, under an ionic conductivity of the aqueous suspension having a stabilized value of 60 mS / cm or higher, a portion of the continuous phase of the suspension is replaced with a third aqueous solution. That is, a portion of the continuous phase of the suspension is drained from the thermostatic reactor in which step iv) is performed, and the third aqueous solution is introduced into the reactor. Typically, the volume of the third aqueous solution introduced is equal to the volume of the drained continuous phase. In one specific embodiment, half of the continuous phase in the reactor is drained.

[0086] The third aqueous solution embodied in the method according to the present invention comprises water as a solvent, thus describing the name of the aqueous solution. Typically, the third aqueous solution embodied comprises only water, that is, it consists of water. Alternatively, it may comprise at least one other element in addition to the solvent which is water. This other element is, in particular, an anti-sticking agent as previously defined. If an anti-sticking agent is present in the third aqueous solution, the anti-sticking agent is used in an amount of 5 mass% or less relative to the mass of the propellant being treated, particularly in an amount of 1 mass% to 3 mass% relative to the mass of the propellant being treated. The composition of the third aqueous solution may be the same as or different from the composition of the first aqueous solution, and may be the same as or different from the composition of the second aqueous solution.

[0087] FIG. 1 illustrates an embodiment in which the third aqueous solution contains only water, that is, is composed of water.

[0088] When a portion of the continuous phase of the suspension is replaced with the third aqueous solution, step iv) is continued, that is, stirring of the resulting suspension is continued until a stabilized value of ionic conductivity is obtained again. Depending on the obtained stabilized ionic conductivity value, step v) will be implemented (value less than 60 mS / cm), or the reactor will be emptied again and a new aqueous solution will be supplied (value greater than 60 mS / cm).

[0089] FIG. 2 illustrates all steps in a method for processing solid composite propellants, among which the method for recovering ammonium perchlorate according to the present invention corresponds to the "maceration extraction" block. Among other blocks, there are steps prior to or following the method according to the present invention, previously described, such as milling and dehydration steps.

Claims

Claim 1 A method for recovering ammonium perchlorate contained in a solid composite propellant, the method comprising: i) contacting the solid composite propellant in the form of fragments with a first aqueous solution; ii) fragmenting the fragments of the solid composite propellant present in the first aqueous solution to obtain fragments of the solid composite propellant having a maximum dimension not exceeding 10 mm; iii) adding a second aqueous solution to the mixture obtained in step ii), wherein the amount of water has a W / P mass ratio of 2.5 to 6.8, and stirring the entire mixture to obtain an aqueous suspension, wherein W represents the sum of the mass of water in the first aqueous solution and the mass of water in the second aqueous solution, and P represents the mass of the solid composite propellant present in the form of fragments; iv) maintaining the stirring for 6 to 15 hours to solubilize the ammonium perchlorate in a continuous phase of the aqueous suspension, wherein the solubilization is achieved by measuring the ionic conductivity of the aqueous suspension A method comprising: a step v) separating the dispersed phase and the continuous phase of the aqueous suspension when the ionic conductivity reaches a stabilized value of less than 60 mS / cm; wherein the stabilized value is a value of ionic conductivity measured in the aqueous suspension that does not change upward or downward by more than 1 mS / cm for a period of more than 60 seconds, and steps (i) to (iv) of the method are performed at the same or different temperatures of 50°C or lower. Claim 2 A method according to claim 1, characterized in that the maximum dimension of the piece of the solid composite propellant used in step i) does not exceed 50 mm. Claim 3 A method according to claim 1 or 2, characterized in that the dimensions of the piece of the solid composite propellant implemented in step i) are less than or equal to the dimensions of a rectangular parallelepiped of 25 mm x 25 mm x 50 mm. Claim 4 A method according to claim 1 or 2, characterized in that the W / P mass ratio is 4. Claim 5 A method according to claim 1 or 2, characterized in that, during step iv), if the ionic conductivity of the aqueous suspension has a stabilized value of 60 mS / cm or more, a portion of the continuous phase of the aqueous suspension is replaced with a third aqueous solution. Claim 6 A method according to claim 1 or 2, characterized in that steps (i) to (iv) are performed at the same or different temperatures of 30°C to 40°C. Claim 7 A method according to claim 5, characterized in that the first aqueous solution, the second aqueous solution and / or the third aqueous solution comprises an anti-adhesion agent. Claim 8 A method according to claim 5, characterized in that the first aqueous solution is composed of water and an anti-stick agent, the second aqueous solution is composed of water, and / or the third aqueous solution is composed of water. Claim 9 A method according to claim 7, wherein the anti-stick agent is selected from the group consisting of talc, glycerol monostearate, kaolin, calcium carbonate, magnesium trisilicate, stearic acid, calcium stearate, magnesium stearate, zinc stearate, glycerol monostearate, glycerol palmitostearate, polyethylene glycol, benenic acid glycerol ester, colloidal silicon dioxide, finely divided silicon dioxide, aluminum hydroxide, hydrogenated vegetable oil, anionic surfactants, nonionic surfactants, and amphoteric surfactants.

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