Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B33/00—Manufacture of ammunition; Dismantling of ammunition; Apparatus therefor
  • F42B33/06—Dismantling fuzes, cartridges, projectiles, missiles, rockets or bombs
  • F42B33/067—Dismantling fuzes, cartridges, projectiles, missiles, rockets or bombs by combustion
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0091—Elimination of undesirable or temporary components of an intermediate or finished product, e.g. making porous or low density products, purifying, stabilising, drying; Deactivating; Reclaiming

Definitions

• the present invention relates to a method for destroying pyrotechnic compounds. It also relates to a device suitable for implementing said method.
• the method and device are particularly useful in soil remediation contexts containing pyrotechnic compounds. They are particularly suitable for treating soils polluted with nitrocellulose.
• the present invention falls within this framework and proposes an original method for destroying pyrotechnic compounds.
• the proposed method makes it possible to overcome the pyrotechnic dangers associated with such operations. It can thus be implemented without danger within a pyrotechnic site or in an urban environment.
• One method of destroying pyrotechnic compounds contained in an aqueous slurry or an aqueous solution consists in composting them in an oxygenated medium so as to degrade them biologically.
• a slurry or aqueous solution containing the pyrotechnic compound (s) manure, vegetable substances, water and wood chips are added. Windrows are aerated by turning them over.
• the large quantities of compost to be treated (it takes about 10 m 3 of added material per 1 m 3 of sludge or aqueous solution) induce heavy handling operations and require large storage.
• An additional difficulty of this method is to maintain, throughout the degradation process, sufficient moisture compost to ensure the decomposition of pyrotechnic compounds.
• Another method relies on the thermal degradation of the pyrotechnic compound (s) contained in a sludge or aqueous solution.
• common pyrotechnic compounds RDX, HMX, nitrocellulose, etc.
• RDX, HMX, nitrocellulose, etc. RDX, HMX, nitrocellulose, etc.
• the sludge or aqueous solutions containing the pyrotechnic compound (s) are directly introduced into the furnace.
• the product placed in the oven first begins to dry before the decomposition of the pyrotechnic compound begins. It therefore presents a pyrotechnic danger during treatment.
• the patent application DE 40 37 919 describes a method of thermally destroying (under aerobic conditions) pyrotechnic compounds. Stable and regular combustion is aimed at leading to complete oxidation in order to limit the production of nitrogen oxides.
• the material to be treated is ground under water, dehydrated and then heated in a fluidized bed in the presence of non-combustible or combustible aggregates, for example of lignite or urea granules.
• propellants and powders mixed with an inert material, such as earth (such earth) can be burned under the same conditions. containing mineral matter and organic matter); it is not described a real inerting in the sense of the invention (implemented under the conditions specified below, before and during the heat treatment).
• the reduction of pyrotechnic hazards related to the destruction of pyrotechnic compounds thermally is also not addressed by this document.
• the patent application DE 296 23 410 relates to a device for destruction by thermal means (destruction in aerobic condition) of pyrotechnic compounds. Before being introduced into an oven, the compounds are inerted by coating with a solution (soap, wax, oil, etc.) that may contain sawdust. They are transported safely from their storage location to the oven.
• the material entering the process (material to be treated) and the material handled during the process (material being processed) must not be classified as a pyrotechnic product.
• a classification can be determined by pyrotechnic sensitivity tests, well known to those skilled in the art, which can vary from one country to another according to local regulations.
• classification is generally determined by means of tests that meet UN standards for the classification of substances for carriage. According to the latter standards, a material designated as inert in the rest of the document is outside the UN class 1 (corresponding to pyrotechnic products).
• the method of the invention makes it possible to thermally destroy at least one pyrotechnic compound, "pure” or contained in an aqueous solution or an aqueous sludge (which may both contain organic materials), by raising the temperature in an oven, without generating pyrotechnic danger.
• a pulverulent material having a melting or decomposition temperature higher than that of the furnace, and therefore also greater than the (highest) decomposition temperature of the pyrotechnic compound (s) is added the said "pyrotechnic” compound (s) "pure (s)” or content (s) in an aqueous sludge or aqueous solution, before its (their) introduction into the oven, and this in quantity sufficient to ensure the inerting of the said pyrotechnic compound (s) considered dry.
• the mixture - pyrotechnic charge added with said powdery material - therefore behaves as an inert product throughout the duration of the process of the invention. It is understood that the mixture in question is a sufficiently homogeneous mixture, advantageously as homogeneous as possible, so that the desired inerting is ensured (in all its mass).
• the (minimal) quantity of powdery material to be added to said charge to be inerted obviously depends on the quantity of pyrotechnic compound (s) present in said charge. and pyrotechnic sensitivity properties of the at least one pyrotechnic compound in question.
• This (minimal) quantity to be added is determined using laboratory tests, well known to those skilled in the art, for measuring the amount of inert material to be added to at least one pyrotechnic compound to ensure its inerting.
• the amount of pulverulent material added is such that its mass represents at least 85% of the sum of the masses of said at least one dry pyrotechnic compound and said added powdery material.
• the mass of pulverulent material added is generally from 90% to 99% of said sum of masses.
• the mass of pulverulent material added determined from the content of pyrotechnic compound (s) in the mud or the aqueous solution, typically represents between 50% and 95% of the total mass introduced into the oven.
• the process of the invention generally comprises (in addition to the two successive stages of mixing and heat treatment mentioned above), with reference to the subsequent heat treatment, a preliminary step of measuring the decomposition temperature of said at least one pyrotechnic compound to be destroyed present in the charge.
• This measurement is advantageously also carried out by thermogravimetry.
• thermogravimetry Nor is it obligatory in certain contexts, for example when the compound or mixture of compounds to be destroyed is perfectly identified (i.e. when its decomposition temperature is already known).
• thermogravimetry one determines both the mass ratio of the at least one pyrotechnic compound to be destroyed within the charge and the decomposition temperature of said at least one compound.
• the oven temperature is obviously adequate for the destruction of the compound having the highest decomposition temperature.
• the powder material used obviously has a sufficiently small particle size to be able to ensure an intimate mixture with said at least one "pure" pyrotechnic compound or contained in a sludge or an aqueous solution.
• the median diameter (the particle size) of said pulverulent material is generally between 0.01 and 5 mm, advantageously between 0.06 and 2 mm.
• Said powder material is chosen from inorganic and organic materials or mixtures thereof. Minerals are particularly preferred. It is advantageously sand (conventionally composed mainly of quartz, granite and mineral salts). The preferred organic material is sawdust. Said powder material is therefore advantageously sand or sawdust. It consists very advantageously of sand. Any other organic or inorganic material may be used, provided, of course, that its melting or decomposition temperature is greater than the maximum temperature of implementation of the process (at the maximum operating temperature of the oven during said process) , and therefore also greater than the decomposition temperature of said at least one pyrotechnic compound (to be destroyed).
• T-decomposition 180 ° C
• other pyrotechnic compounds such as in particular RDX, HMX, CL20, nitroglycerin and solid propellant fragments.
• it is suitable for the destruction of any pyrotechnic compound and mixture of pyrotechnic compounds, insofar as a pulverulent material, capable of ensuring inerting and having an adequate melting temperature or decomposition, exists.
• the method of the invention can be implemented continuously or sequentially.
• the heat treatment of the process of the invention is implemented under aerobic conditions.
• This first variant may also be suitable for "pure" pyrotechnic compounds, but in this case, the second variant described below is preferred.
• the furnace is brought to a temperature sufficient to ensure the destruction by combustion of the at least one pyrotechnic compound and said material. organic (included in the aqueous slurry or in the aqueous solution) contained in the mixture introduced into the oven.
• the heating of the oven is adjusted so that the temperature of the products at the outlet of the oven is between 250 and 450 ° C. This imposes a temperature in the furnace certainly high enough (up to 1000 ° C locally) to lead to the destruction of said at least pyrotechnic compound and said organic material.
• the powder material suitable for carrying out the process according to this variant is a mineral material, advantageously sand.
• the combustion destruction of said at least one pyrotechnic compound and said organic material at this elevated temperature produces gases and particles.
• the powder material can indeed break mechanically in the oven.
• Fine dust of said powder material can therefore also be produced.
• These emissions make it necessary to associate the oven with ventilation connected to an evacuation outlet extended by a chimney (chimney often incompatible with an urbanized environment) equipped with particulate filters and a post-combustion gas treatment device.
• the soiled pulverulent material is recovered by non-discharged residues, carbonized combustion products, originating from the organic material and by mineral elements coming from the mud or of the aqueous solution. Said soiled powdery material can be recycled in the process or repelled according to its state.
• the heat treatment of the process of the invention is carried out under anaerobic or quasi-anaerobic conditions (ie in large oxygen deficiency with respect to a stoichiometric combustion equilibrium) at a lower temperature.
• the furnace is brought to the decomposition temperature of the at least one pyrotechnic compound to be destroyed, typically between 180 ° C and 350 ° C for the common pyrotechnic compounds, or at a temperature similar to slightly above + 50 ° C maximum) at said decomposition temperature.
• the powder material can be chosen not only from mineral materials but also from mixtures of organic and inorganic materials and from organic materials.
• a treatment product comprising the powdery material, the undecomposed dry organic matter, if said material was present in the sludge or solution, is recovered.
• aqueous starting material and the solid decomposition products of said at least one pyrotechnic compound According to a first route more particularly chosen when the powdery material is inorganic, said powdery material may be separated from the treatment product and recycled or scraped according to its state and said organic matter and the solid decomposition products of said at least one pyrotechnic compound dry or rehydrated can be bio-dumped or redeposited at the sampling site.
• said treatment product can be disposed completely in bio-discharge or redeposited at the place of sampling in the dry state or rehydrated.
• the treatment product (recovered in the end process) is thus, advantageously, either partially or wholly, recovered in composting brio-discharge or delivered (recycle) at the place of sampling of said at least one pyrotechnic compound.
• the advantage of this variant is that it does not generate large quantities of gas and particulate emissions, and therefore does not require an emission processing device associated with the furnace.
• Ventilation connected to an exhaust vent only with activated carbon filters and particulate filters is required to trap products (eg volatile organic compounds and / or dust) that may be emitted at ambient temperature.
• “low” oven operation (less than 500 ° C, usually less than 400 ° C).
• the invention relates to a device suitable for implementing the method of the invention, as described above.
• This device comprises a mixer, for example of the concrete mixer type, for mixing (effectively) the charge to be treated with said powder material and an oven.
• a mixer for example of the concrete mixer type
• the product introduced into the oven from settling by gravity and / or to prevent the formation of a dried mud shell which makes a thermal barrier limiting the degradation of the pyrotechnic material
• the device of the invention is advantageously equipped with an original measurement means: a macro thermobalance, in particular of the type described in the reference " Thermal analysis of energy crops, Part I.
• a macro-thermobalance in particular of the type described in the reference " Thermal analysis of energy crops, Part I.
• the applicability of a macro-thermobalance for biomass studies ", Khalil RA et al., Journal of Analytical and Applied Pyrolysis, 2008, 81, No. 1, pp. 52-59 , using the method of determination by thermogravimetry known to those skilled in the art and in particular allowing rapid measurement (in 15 to 30 s), on representative sample masses (500 g per analysis), the rate of compound (s) pyrotechnic (s) content (s) in a sludge or aqueous solution and thus to determine the amount of powder material to be added.
• This measuring instrument is adapted to the temporal sequence of the process, unlike the usual laboratory methods (for example chromatography) requiring several hours of analysis.
• the principle consists in heating the sample arranged in thin layers on several trays so as to determine by weighing, at 100 ° C, the amount of water evaporated, then at a higher temperature, at the decomposition temperature of the at least one compound pyrotechnic, the amount of said at least one decomposed pyrotechnic compound.
• This analysis is advantageously also carried out at the outlet of the oven so as to ensure that the pyrotechnic compound has been destroyed.
• the outlet of the oven can be provided simply with activated carbon filters and particles (low temperature implementation variant) or extended by a chimney equipped with particulate filters and a means of gas afterburning (variant implementation at high temperature).
• the method of the invention is implemented in a device as described above.
• Said example relates to the implementation of the method of the invention according to its first variant (in aerobic condition, "at high temperature"), for the destruction of nitrocellulose (pyrotechnic compound of class 1) contained in a pool of a industrial pyrotechnic site operated for over a hundred years.
• the mass of nitrocellulose contained in said basin is about 8000 t.
• the products recovered in said basin consist of sludge (based on sand, pebbles) aqueous or aqueous solutions that may contain organic material, mainly of plant origin.
• concentration of nitrocellulose in said recovered and dried products ranges from 100% (the product recovered is then composed of water-soaked nitrocellulose fibers) to 0% depending on the location of the sample. It may happen that the recovered products do not contain, locally, nitrocellulose.
• the mud is drawn from the basin by a mechanical shovel and declawed (we remove the large stones, branches ...) and deposited on a concrete slab. After natural spinning, the residual water content is at least 70%.
• a representative sample (sludge) with a mass of 500 g is analyzed by means of a macro thermobalance to determine the level of nitrocellulose contained in its volume. It is to be treated according to the invention. The quantity of powdery material to be added to said sample, so as to ensure the inerting of the charge in the oven, can then be determined.
• the powder material added is fine sand, washed.
• the median diameter of the particles of said sand of about 1 mm.
• the quantity (mass) of sand added represents 90% of the sum of the masses of dry nitrocellulose and added sand (inerting is thus ensured), hence the importance of a rapid and reliable measurement of the nitrocellulose content .
• the mixing process between the slurry containing nitrocellulose and sand is discontinuous: it is done in a concrete mixer (600 Kg per batch), as is used in plants where cement is prepared.
• the oven used is a rotary kiln.
• the quantity of material introduced per hour in the oven is 3 to 3.5 tons.
• the residence time in the oven is about 20 minutes.
• the oven is cleaned periodically.
• the time intervals between each cleaning of the furnace are variable (of the order of the month generally, but this is more frequent when the treated sludge contains clay (the clay when drying is a crust on the walls of the oven).
• the furnace is thermally powered by a gas burner and its power is modulated so that at the outlet of said furnace, the temperature of the sand and carbonized organic matter residues is 250 ° C. to 450 ° C., which guarantees the destruction nitrocellulose.
• the temperature in the oven can then rise locally up to 1000 ° C.
• a high-flow fan (5000 m 3 / h) provides, via a vent, the extraction in a chimney of gaseous and particulate combustion products produced by the combustion of organic matter (sludge) and the compound pyrotechnic.
• the mechanical effect caused by the rotation of the furnace can also lead to breaking of sand particles. These small particle size breaks can also be carried away by the extraction means.
• the products, after such (first) treatment, consist, at the outlet of the oven, of sand containing from 3 to 5% of carbonized organic matter.
• the sand turned black (it was a dirty white color originally). It does not contain any pollutant.
• a measurement of the (residual) rate of pyrotechnic compound (nitrocellulose) is carried out (by means of macro thermobalance) on the products after treatment, in order to ensure the smooth running of the process and its efficiency.
• Post-treatment products can be reused in the process.
• the sand is replaced periodically (typically after a few days of implementation of the process), when it contains too much carbonized organic matter dust or that its particle size has decreased too much mechanically in the oven.
• the non-recycled sand in the process is stored on site and discharged into the sludge basin containing nitrocellulose.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• General Engineering & Computer Science (AREA)
• Treatment Of Sludge (AREA)

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Citations (5)

• 2010
  • 2010-05-12 FR FR1053717A patent/FR2960056B1/fr not_active Expired - Fee Related
• 2011
  • 2011-05-10 EP EP11165514.8A patent/EP2386821B1/de active Active

Patent Citations (5)

Non-Patent Citations (1)

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