Plastic and nonmetallic article shaping or treating: processes – Explosive or propellant article shaping or treating – Forming or treating particulate material
Patent
1994-03-07
1997-04-22
Nelson, Peter A.
Plastic and nonmetallic article shaping or treating: processes
Explosive or propellant article shaping or treating
Forming or treating particulate material
264 34, 149111, 149115, C06B 2100, A45C 102
Patent
active
056231687
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of and an apparatus for reducing the grain size of crystalline explosive, especially hexogen or mixtures containing hexogen, wherein the explosive is dissolved in an organic solvent, the dissolved explosive subsequently is precipitated and crystallized in the presence of water, and then the resulting recrystallized explosive is separated from solvent and water.
In the context of the present application, crystalline explosive, in the first place, is understood to be hexogen (RDX), also octogen (HMX) and nitropenta (PETN), but also any other explosive which is available in crystalline form as well as mixtures of such explosives.
The final product in the preparation of hexogen and other crystalline explosives is obtained in coarse crystalline form. For many cases of application, however, the crystalline explosive is required to be in fine crystalline form, especially if it is a constituent of a propellant charge powder.
In the case of a known method of reducing the grain size, the crystalline explosive is ground in a mill while liquid is being added. The mechanical crushing of the violent explosive is to be classified as dangerous in spite of the addition of liquid. Moreover, with the known method, the separation of the fine fraction can be accomplished with difficulty only.
A method of the kind mentioned initially is already known from European patent application 0 340 188 by means of which the average grain size of hexogen and other crystalline explosives can be reduced to a mean particle size of less than 20 micrometers. With the known method, the explosive, such as hexogen is dissolved in a solvent and water at a temperature between 60.degree. C. and 70.degree. C. and while being stirred. The explosive solution is conveyed into a steam ejector, while being pressurized by nitrogen. In the ejector, crystallization takes place, the solvent evaporating and the explosive precipitating. The precipitated crystalline explosive then is separated in a downstream cyclone. A mean particle size of 8 micrometers is said to be obtainable by the known process.
It is the object of the invention to propose a method and an apparatus by means of which very small grain sizes can be obtained and with which a very high degree of safety in application is achieved.
SUMMARY OF THE INVENTION
The above and other objects of the invention are achieved by the provision of a method which comprises the steps of dissolving the explosive in an organic solvent, precipitating the dissolved explosive by bringing the dissolved explosive together with cold water, while turbulently agitating the mixture of the explosive, water, and solvent, and then separating the resulting precipitated explosive from the solvent and the water. In accordance with the present invention, the precipitating step includes adding a precipitant to the mixture to retard crystal growth and which is selected from at least one of the group consisting of (1) a decomposition product of starch, (2) derivatives of starch or cellulose which are soluble in water, and (3) greatly diluted solutions of different sugars. Also, the separating step includes adding a wetting agent to the mixture of the explosive, water, and solvent, before and/or during the separation to prevent agglomeration of the solid particles.
The method according to the invention provides for the explosive solution to be brought together with cold water. Under turbulent agitation, the precipitation and crystallization of the explosive take place. The explosive is yielded in fine crystalline form. In the case of hexogen, mean grain sizes of from 4 to 6 micrometers can be obtained by the method according to the invention. The resulting final product, which still needs to be separated from solvent and water after crystallization, is characterized by great handling safety. The method according to the invention, furthermore, offers a high degree of safety in application.
According to a further development of the invention the cold water has a temperatu
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Ewald Gerhard
Fels Gregor
Nelson Peter A.
Wasagchemie Sythen GmbH
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