Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
1998-01-05
2002-05-14
Griffin, Steven P. (Department: 1754)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C588S253000
Reexamination Certificate
active
06388164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of treatment of hazardous waste for disposal. More particularly, it relates to a method of treating high explosives and related energetic materials via base hydrolysis to render them non-explosive and/or non-energetic.
2. Description of Related Art
The end of the Cold War has brought a concomitant need for the treatment and disposal of large inventories of high explosives and associated high explosives waste, particularly in the United States, Europe, and countries of the former Soviet Union. Under the terms of numerous treaties such as the Intermediate-range Nuclear Forces Treaty and the Strategic Arms Reduction Treaties, stockpiles of weapons, including nuclear weapons, must be dismantled and/or demilitarized (Heilmann et al., 1994). These demilitarization activities generate large amounts of high explosives, including 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane (HMX), 1,3,5-triaza-1,3,5-trinitrocyclohexane (RDX), and 2,4,6-trinitrotoluene (TNT), as well as explosives-contaminated processing water, soils and groundwater.
At the end of 1992, the United States Department of Defense possessed more than 317,000,000 kg of high explosives requiring treatment and disposal (Byrd and Humphreys). The majority of these explosives were RDX- and TNT-based. Through the dismantlement of nuclear weapons, the United States Department of Energy generates an additional 50,000 kg per year of high explosives waste, most of which is HMX-based.
Currently most high explosives are treated by the method of open burning/open detonation. In fiscal year 1992, 80% of the 56,000,000 kg of high explosives demilitarized by the United States Department of Defense were treated by this method (Byrd and Humphreys).
Alkaline hydrolysis of high explosives has been identified as a possible alternative to open burning/open detonation technology (Spontarelli et al.). In this approach, high explosives are typically placed in a molar excess of aqueous base solution and the mixture is heated and agitated for several hours until all high explosives have been hydrolyzed. However, the extremely low solubility of high explosives in water limits the rate of this reaction, and the usefulness of this method for large scale processing of high explosives is correspondingly limited. For example, the solubility of HMX in water at 90° C. is only about 286 parts per million (ppm). This means that in the alkaline hydrolysis of HMX, only a tiny fraction of the explosive is solvated and available for contact and reaction with aqueous base at any given time. In order to treat large amounts of high explosives in a timely manner, extremely large reaction vessels containing similarly large amounts of aqueous base solution are therefore required, making the alkaline hydrolysis process both unwieldy and prohibitively costly. Furthermore, the alkaline hydrolysis of explosives is difficult to control precisely because the explosives are added in solid (granular) form directly to an aqueous base solution in which they are only sparingly soluble. This can lead to localized exotherms in the reaction mixture, causing foaming and other undesirable phenomena, such as an uncontrollably rapid reaction.
SUMMARY OF THE INVENTION
The present invention overcomes problems in the prior art by providing a method for treating high explosives in which the explosives are fully dissolved prior to a hydrolysis step, thus permitting good contact of the explosives with aqueous base, resulting in a rapid hydrolysis reaction which proceeds to completion. Advantageously, because the explosive is already fully dissolved prior to addition to the base solution, the rate of the hydrolysis reaction is exponentially faster, permitting the use of lower reaction temperatures if necessary. Another advantage of the method of the present invention is that a more concentrated base mixture may be employed, thus allowing a reduction in equipment size and further allowing a reduction in the number of times the base solution must be changed out.
In one broad respect, this invention is a method for treating explosive materials to render them non-explosive. In another broad respect, this invention is a method for treating energetic materials, such as rocket fuels, to render them non-energetic. In this application, the terms “explosive” and “high explosive” are used interchangeably, and are defined as a substance usually characterized by chemical stability but which may be made to undergo rapid chemical change without an outside source of oxygen, whereupon a quantity of energy, usually accompanied by hot gases, is evolved. As used herein, the term “energetic material” is defined as any chemical compound which, when subjected to heat, impact, friction, shock, or other suitable initiation, undergoes a very rapid chemical change with the evolution of large volumes of heated gases that exert pressure in or on the surrounding medium.
In the practice of one typical embodiment of the present invention, an explosive is dissolved in a polar, aprotic organic solvent to form an explosive-containing solution. The explosive-containing solution is added to a basic aqueous solution to form a reaction mixture, such that a hydrolysis reaction may occur between the explosive and the base. Typically, the reaction mixture is stirred and maintained at a temperature sufficient to ensure that the hydrolysis reaction proceeds to completion. An amount of aqueous acid solution sufficient to neutralize the aqueous base is then added to the reaction mixture. Gaseous products of the hydrolysis reaction may be scrubbed prior to venting to the atmosphere, if necessary. The remaining reaction mixture, including hydrolysis products, then is filtered to remove any solids, including unreacted material, which may be present. If this solid residue contains any unreacted explosives, it may be added to another batch of explosives to be dissolved in a polar, aprotic solvent. If no explosives are present in the solid residue, it may be drummed and disposed as waste. The remaining liquid phase of the reaction mixture may be evaporated to remove any salts and distilled to separate any liquid hydrolysis products from the aqueous phase and the polar, aprotic organic solvent phase. Finally, the aqueous phase and the polar, aprotic organic solvent phase may be, at least partially, reused or recycled in subsequent batches of the inventive base hydrolysis method.
In one embodiment, the present invention is a method for hydrolyzing an explosive, including the steps of dissolving the explosive in a polar, aprotic organic solvent to form an explosive-containing solution, and adding the explosive-containing solution to a basic aqueous solution to form a mixture or reaction mixture, such that the explosive is hydrolyzed. In certain specific embodiments of the present invention, the polar, aprotic organic solvent is dimethylsulfoxide, and the reaction mixture comprises from about 65% to about 85% dimethylsulfoxide by volume.
Explosives which may be treated by the method of the present invention include, but are not limited to, 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane, 1,3,5-triaza-1,3,5-trinitrocyclohexane, 2,4,6-trinitrotoluene, or mixtures the three.
In embodiments of the disclosed invention in which the explosive is 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane and the solvent is dimethylsulfoxide, the explosive-containing solution comprises preferably less than about 450 g 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane per liter of dimethylsulfoxide, and more preferably from about 200 g to about 280 g 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane per liter of dimethylsulfoxide.
In embodiments of the disclosed invention in which the explosive is 1,3,5-triaza-1,3,5-trinitrocyclohexane and the solvent is dimethylsulfoxide, the explosive-containing solution comprises preferably less than about 460 g 1,3,5-triaza-1,3,5-trinitrocyclohexane per liter of dimethylsulfoxide, and more preferably from about 200 g to about 280 g 1,
Cates Dillard M.
Desmare Gabriel W.
Fulbright & Jaworski LLP
Mason & Hanger Corporation
Nave Eileen E.
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