WO1995034797A1

WO1995034797A1 - Method for removing explosives from ammunition parts

Info

Publication number: WO1995034797A1
Application number: PCT/SE1995/000722
Authority: WO
Inventors: Stefan Lamnevik
Original assignee: Forsvarets Forskningsanstalt; Forsvarets Forskningsanstalt (FOA)
Current assignee: Forsvarets Forskningsanstalt; Forsvarets Forskningsanstalt (FOA)
Priority date: 1994-06-14
Filing date: 1995-06-14
Publication date: 1995-12-21
Anticipated expiration: 1996-12-14
Also published as: SE9402092D0; AU2759695A; SE508313C2; SE9402092L

Abstract

A method for removing explosives, including metal-powder-containing explosives, which contain at least one meltable component, from ammunition parts by flushing a heating medium in direct contact with the explosive and recovering the explosive mixed with the heating medium. As heating medium, a combustible substance is selected, which is in the liquid state at the process temperature concerned and which has no available oxygen or only alow content thereof. The combustible substance may consist of hydrocarbons, alcohols, ketones, esters and mixtures thereof. Suitable readily available substances are fuel oil, lubricating oil and meltable wax. The recovered mixture of explosive and heating medium can be processed to a liquid/suspension suitable for combustion, as disclosed in WO 93/17295.

Description

Method for removing explosives from ammunition parts.

The invention relates to a method for removing explosives, which contain at least one meltable component, from ammunition parts. More specifically, the invention relates to melting-out and flushing-out the explosive with the aid of a heating me¬ dium/flushing medium which is brought in direct contact with the explosive.

In the destruction of ammunition, it is essential that explosives included in the am¬ munition can be separated from other materials, such as metal casings. The most common requirement is to remove high explosives from warheads such as shells, mines etc. Most such high explosives have been cast into the warhead and contain trinitrotoluene (TNT) as the main component. Trinitrotoluene melts at about 80°C and can be cast into or out of warhead casings. Also mixed explosives containing other solid components, trinitrotoluene being the main component, can be cast. Of frequent occurrence are, for instance, hexogen (RDX) or octogen (HMX), which can be suspended in molten trinitrotoluene and be cast into and out of warhead casings in the form of a suspension. Metal powder, above all aluminium and magnesium, is also common in cast explosives.

For removing meltable explosives from warheads, use is today made of heating of the entire ammunition part to a temperature above the melting point of the meltable component. Heating is normally carried out in a furnace, water bath or the like. A variant of such a process is disclosed in German Patent Specification 1,678,212. For large warheads, melting-out in this manner takes a long time - several days for e.g. a large naval mine. For old ammunition, such a long heating time may involve a risk of self-ignition. Besides, the long time is disadvantageous from the aspect of work.

It is obvious to use hot water above 80°C and flush out such meltable explosive substances by means of pumps and nozzles. This technique is also applied to some extent. The flushing technique entails mechanical working of the explosive, at the same time as efficient heat transfer is obtained by the direct contact of the heating medium with the explosive. The removal of the explosive therefore is con¬ siderably quicker as compared with melting-out by heating the entire warhead. However, the method has a serious limitation since the heating medium, the water, will come into direct contact with the explosive. Metal-powder-containing explosives, which are frequently used in above all naval warheads, react with water while de¬ veloping heat with the ensuing risk of self-ignition of the explosive. It has therefore not been possible to use this technique for melting out metal-powder-containing explosives.

An object of the present invention is to provide an improved method for removing explosives from ammunition parts, which eliminates the above-mentioned draw¬ backs of known methods.

This is achieved by a method as defined in the claims.

The invention relates to a method for removing explosives containing at least one meltable component from ammunition parts by flushing a heating medium, heated to a selected process temperature, in direct contact with the explosive, and recover¬ ing the explosive mixed with the heating medium. According to the invention, a combustible substance, which is in the liquid state at the process temperature and has no available oxygen or only a low content thereof, is selected as heating me¬ dium.

The method is applicable primarily to cast explosives which are castable precisely owing to the presence of a meltable component, but also press-moulded explo- sives, which have been made compressible for instance by admixing wax, can be removed by melting and dissolving the wax component, thereby permitting flushing- out of the explosive.

In the method, the combustible substance is flushed directly against the explosive, which is then successively loosened and, mixed with the combustible substance, conveyed out of the ammunition part. Loosening occurs as the meltable component melts and/or dissolves in the combustible substance.

By the fact that the explosive is mixed with a substance having no available oxygen or only a low content thereof, the risk that the explosive will detonate is reduced. The ability of an explosive to explode is primarily determined by its chemical com¬ position, especially its balance between oxygen and other chemical elements. By adding, when flushing out the explosive, a sufficiently large quantity of other sub¬ stances which displace the oxygen balance of the explosive in the oxygen lean di- rection, the resultant mixture can no longer detonate. Such substances are liquid combustible substances which have no intrinsically available oxygen or only a low content of available oxygen. The combustible substance should thus lack oxygen bound as peroxide, nitro group, nitrate group nitramine group etc. Suitable combus- tible substances are hydrocarbons, alcohols, ketones, esters and mixtures thereof. Suitable mixed substances are, for instance, different petroleum fractions which are liquid at the process temperature involved and thus can be flushed against the ex¬ plosive and function as conveying liquid for removing the explosive from the am- munition part. Such substances can also be used in direct contact with metal-pow¬ der-containing explosives, for instance those containing aluminium or magnesium powder, without any negative side-reactions occurring.

The heating medium is selected in view of what temperature is the process tem- perature in the case concerned and in view of how the recovered mixture should be further processed, for instance for recovery of the explosive components or for de¬ struction.

Since most cast explosives contain trinitrotoluene as meltable component, and trini- trotoluene has a melting point of about 80°, the heating medium should in many cases have a temperature of 80-110°C in the process. Many organic substances which can be used as heating medium, however, have the ability of dissolving trini¬ trotoluene, and therefore process temperatures below the melting point of trinitro¬ toluene can also be used. However, the solubility increases as the temperature in- creases, and consequently some heating is preferred.

Easily available substances which are suitable as heating medium according to the invention are fuel oils, and use can be made of both light and heavy fuel oil, mineral oils such as lubricating oils, and meltable waxes. Fuel oils are especially attractive to use when the explosive is to be destroyed, which may advantageously be carried out as disclosed in International Patent Application WO 93/17295. WO 93/17295 discloses a method of destroying explosives by converting them to a pumpable liq¬ uid or suspension which is nondetonatable but combustible and can be burned in conventional furnaces. The explosive is dissolved or suspended in a combustible liquid which has no available oxygen or only a low content of available oxygen, the proportion of liquid being so large as to reduce the energy content of the mixture to 1 MJ/kg or less in the absence of available atmospheric oxygen. The same liquid as used to dissolve or suspend the explosive for destruction can, according to the pre¬ sent application, be used as heating medium when flushing out the explosive from the warhead. The mixture of explosive and heating medium obtained in the flush¬ ing-out process can be directly used for preparing a destroyable liquid/suspension according to WO 93/17295. The invention will be exemplified with reference to Fig. 1 which schematically shows a system for flushing out an explosive from an ammunition part.

The Figure shows an example of removing a cast explosive 2 from a shell 1 , from which the bottom screw has been removed. The heating medium is sprayed against the explosive through a lance 3, which is inserted through the opening in the shell bottom. In order to avoid vapours and aerosols in the ambient air, it may be conven¬ ient to carry out the process in a closed system. The opening of the shell can be sealingly connected to an outlet conduit 4 and the lance for injecting the combusti- ble substance can be axially displaceable in the outlet conduit. As the explosive melts and is loosened from the cast charge, it is conveyed out of the shell, mixed with the combustible substance. The mixture, which may contain more or less large aggregates of non-molten explosive, non-meltable explosive components, metal powder etc., is conducted to processing which is schematically shown to be a block 5.

Such processing may comprise separating steps such as sedimentation, filtration and centrifugation and steps for precipitation and granulation of the molten compo¬ nent etc. in order to recover the different components from the explosive. Molten components, for instance trinitrotoluene which is emulsified in the heating medium, can be crystallised out by cooling the mixture.

The heating medium can be recirculated via a tank 6, in which fresh heating me¬ dium (make up) is added through a conduit 7 and heating to the process tempera- ture occurs. From the tank 6, the heating medium is pumped via conduits to the lance 3.

In many cases, it is not suitable to recover the components in the explosive, for ex¬ ample owing to age and chemical changes, and instead the explosive must be de- stroyed. A solution or suspension suitable for combustion can then be prepared ac¬ cording to WO 93/17295. The same substance as used as heating medium can be used as solvent/suspension medium in the liquid adapted to combustion. The proc¬ essing of the recovered mixture of explosive and heating medium can then be re¬ stricted to providing a homogeneous mixture and adjusting the particle size of sus- pended components. Adjustment of the particle size can be carried out by, for in¬ stance, wet grinding of the explosive in the heating medium.

Claims

Claims:

1. A method for removing explosives, containing at least one meltable component, from ammunition parts by flushing a heating medium, which is heated to a selected process temperature, in direct contact with the explosive and recovering the explo¬ sive mixed with the heating medium, characterised by selecting as heating medium a combustible substance, which is in the liquid state at the process temperature and has no available oxygen or only a low content thereof.

2. The method as claimed in claim 1, characterised in that the combustible sub¬ stance is selected from a group consisting of hydrocarbons, alcohols, ketones, esters and mixtures thereof.

3. The method as claimed in claim 2, characterised in that the combustible substance is fuel oil.

4. The method as claimed in claim 3, characterised in that the combustible substance is heavy fuel oil.

5. The method as claimed in claim 2, characterised in that the combustible substance is lubricating oil.

6. The method as claimed in claim 2, characterised in that the combustible substance is a meltable wax.

7. The method as claimed in claim 1 , characterised in that the explosive contains metal powder.

8. The method as claimed in claim 1, characterised in that the meltable component is trinitrotoluene.

9. The method as claimed in claim 1 , characterised in that the explosive is sepa¬ rated from the mixture, and that the heating medium is recirculated.

10. The method as claimed in claim 1, characterised in that the mixture of explosive and heating medium is processed to a liquid/suspension suitable for combustion.