Abstract:
A system for chemically disposing energetic material enclosed in assembled devices includes a porous basket. The porous basket forms an enclosed chamber for receiving the assembled devices. Further, the basket is supported by a rotatable basket arm that is, in turn, connected to a lifting arm. In addition to these structures, the system includes a tank that holds a hydrolysis solution. The tank is positioned to allow the lifting arm to submerge the basket into the solution. After submersion, the basket arm rotates the basket in the solution to flow the hydrolysis solution into contact with the assembled devices therein. As a result, the assembled devices react with the solution so that the solution penetrates the assembled devices, allowing the solution to contact and react with the energetic material to render the energetic material non-energetic.

Description:
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. F08630-02-C-0083 awarded by the United States Air Force. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains generally to the destruction of munitions or other devices containing enclosed energetic materials. In particular, the present invention pertains to the destruction of such materials via hydrolysis. The present invention is particularly, but not exclusively, useful as a system and method for chemically disposing energetic materials enclosed in assembled devices without pretreatment of the assembled devices. 
     BACKGROUND OF THE INVENTION 
     Destruction of devices containing energetic materials such as explosives, munitions and propellants is a hazardous operation. Often, energetic materials are mechanically removed from these devices. For instance, such materials may be removed by “autoclave melting out” or “steaming out.” However, these processes cannot be used for energetic materials having high melting points, or those energetic materials which ignite before they melt. Another mechanical process used to remove energetic materials is fluid washout by cavitating or non-cavitating high pressure jets. The cavitating jet process involves the impact of vapor bubbles on the devices and may create uncontrolled reactions in the energetic material. Further, non-cavitating fluid jets typically do not operate at pressures that are adequate for efficient erosion of the energetic material. In addition, both of the jet processes use extensive amounts of water, which may be undesirable in certain environments. In other instances, the energetic material may be disposed of by open burning, open detonation, or incineration. However, such methods are not preferred due to the resulting pollution. 
     While these and other methods are generally effective, they do not obviate the danger involved in mechanically operating on devices encapsulating energetic material. In light of the above, it is an object of the present invention to provide a system and method for chemically disposing energetic material enclosed in assembled devices. Another object of the present invention is to provide a system and method for disposing energetic material enclosed in assembled devices with minimal pretreatment of the devices and without detonating or igniting the energetic material. Another object of the present invention is to provide a system and method for disposing energetic material enclosed in assembled devices without mechanically operating on the devices. Another object of the present invention is to provide a system and method for disposing of energetic materials enclosed in assembled devices in which the assembled devices are chemically penetrated to allow access to the energetic material. Still another object of the present invention is to provide a system and method for disposing of energetic materials in assembled devices in which the energetic material is exposed only within a hydrolysis solution. Yet another object of the present invention is to provide a system for disposing energetic material enclosed in assembled devices which is simple to operate, relatively easy to manufacture, and comparatively cost effective. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a system for chemically disposing energetic material enclosed in assembled devices comprises a porous basket for receiving the devices. For the present invention, the basket is connected to a basket arm for rotation about a basket axis. Further, the basket is connected to a lifting arm for moving the basket into and out of a tank holding a caustic or acidic hydrolysis solution. For the present invention, the basket is submerged in the hydrolysis solution by the lifting arm and is rotated therein by the basket arm. Preferably, a caustic hydrolysis solution is between approximately 60° C. and approximately 130° C. and between about 4 wt. % and about 50 wt. % sodium hydroxide. Further, an acidic hydrolysis solution is preferably between approximately 50° C. and approximately 80° C. and between about 3M and about 8M nitric acid. 
     Upon submersion of the devices in the hydrolysis solution, the solution flows into contact with the assembled devices to facilitate a reaction. During the reaction between the assembled devices and the hydrolysis solution, the assembled devices are penetrated by the hydrolysis solution. As a result, the hydrolysis solution contacts and reacts with the energetic material to render the energetic material non-energetic. 
     For the present invention, the system further includes a rinse fluid housed in a container. In order to use the rinse fluid, the lifting arm is adapted to remove the basket from the hydrolysis solution after the energetic material is rendered non-energetic, and to immerse the basket in the rinse fluid. Similar to its use with the hydrolysis solution, the basket arm is adapted to revolve the basket in the rinse fluid to rinse off components remaining in the basket. 
     As an additional component, the system includes a heat exchanger for selectively adding and removing heat from the hydrolysis solution. By modulating the temperature of the solution with the heat exchanger, the reaction rate can be controlled. Alternatively, or additionally, the solution temperature and reaction rate may be controlled by selectively adjusting the surface area of the solution. Specifically, the system includes surface objects, such as floats, that may be positioned on or removed from the surface of the solution. As a result, the exposed surface area of the solution is selectively increased or decreased. In this manner, the evaporation rate and temperature of the solution are controlled. 
     For purposes of the present invention, the system also includes an exhaust hood for capturing hydrogen or other gases that are released during the hydrolysis process. In order to prevent a build up of the gases to explosive levels, the system is provided with a diluting device that mixes air into the gases to dilute them to non-explosive concentrations. Further, the exhaust hood is provided with an exhaust vent to eliminate gases from the hood. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG. 1  is a schematic view of the system for disposing energetic material enclosed in assembled devices in accordance with the present invention; 
         FIG. 2  is a perspective view of a partially corroded assembled device in accordance with the present invention; and 
         FIG. 3  is an operational flow chart of the method for disposing of energetic material enclosed in assembled devices in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1 , a system for chemically disposing energetic material enclosed in devices such as munitions and propellants in accordance with the present invention is shown and generally designated  10 . As shown, the system  10  includes a tank  12  holding a hydrolysis solution  14 . As shown in  FIG. 1 , the system  10  further includes a perforated or porous basket  16  that may be completely submerged within the solution  14 . Specifically, the basket  16  is mounted on a lifting arm  18  that is adapted to transport the basket  16  into and out of the solution  14 . Further, the basket  16  is connected to a basket arm  20  that is provided to rotate the basket  16  about a basket axis  22 . For the purposes of the present invention, the porous basket  16  forms an enclosed chamber  24  for receiving and holding munitions, cartridge-activated devices, or other assembled devices  26  that enclose energetic material  27  (shown in  FIG. 2 ) including propellants, explosives, smokes or dyes. The porosity of the basket  16  allows the solution  14  to enter the basket  16  and contact the devices  26  while holding the devices  26  within the chamber  24 . Upon contact, the devices  26  react with the solution  14  within the basket  16  and eventually penetrate the devices  26  to react with, the energetic material  27 . 
     For the purposes of the present invention, it is important to keep the basket  16  completely submerged to maintain the continual moderating effect of the solution  14 . If a portion of the basket  16  emerges from the solution  14  during the reaction of the devices  26 , then energetic material  27  can adhere to the wall of the tank  12  or otherwise be pulled out of the solution  14 . Without the moderating effect of the solution  14 , the heat of the hydrolysis reaction can ignite or detonate the unreacted energetic material  27 . 
     For a caustic hydrolysis solution  14 , the solution  14  preferably contains between approximately 4-50 wt. % sodium hydroxide. Preferably, a solution  14  containing sodium hydroxide is kept between approximately 60-130° C. For an acidic hydrolysis solution  14 , the solution  14  preferably contains between about 3M and about 5M nitric acid and is kept between approximately 50-80° C. While sodium hydroxide and nitric acid are expressly disclosed herein, other bases or acids could be used. 
     In order to keep the solution  14  at a desired temperature, the system  10  is provided with a controller  28  and a heat exchanger  30 . Specifically, the controller  28  is able to monitor the temperature of the solution  14  and to operate the heat exchanger  30  to increase or decrease the temperature as needed. Additionally or alternatively, the temperature of the solution  14  may be controlled by manipulating the exposed surface area of the solution  14 . As shown in  FIG. 1 , the solution  14  has an exposed surface  32  which has an area. Because evaporation of the solution  14  can only occur at the surface  32 , controlling the amount of surface area available for evaporation allows for control of the temperature of the solution  14 . With this in mind, the system  10  is provided with surface objects  34 , such as floats, that serve to reduce the surface area available for evaporation. As with the heat exchanger  30 , the placement of the surface objects  34  on the surface  32  of the solution  14  may be controlled by the controller  28 . 
     When the solution  14  evaporates from the surface  32  it is captured by an exhaust hood  36  that is positioned over the tank  12 . In order to recycle the solution  14  that evaporates from the surface  32 , the system  10  is provided with a condensation device  38  that condenses the solution  14  in vapor form, and returns the condensed solution  14  back to the tank  12  via a condensation return  40 . For the present invention, the exhaust hood  36  also captures hydrogen and/or other gases released as a result of reactions within the solution  14 . In order to prevent a build up of these gases to explosive levels, the system  10  is provided with a diluting device  42  that mixes air into the gases to dilute them to non-explosive concentrations. Also, condensable components of the gases, such as water, may be condensed and returned to the solution  14  via the condensation return  40 . Further, the exhaust hood  36  is provided with an exhaust vent  44  to provide for the elimination of gases. 
     As stated above, the basket arm  20  is provided to rotate the basket  16  in the solution  14 . Operationally, the basket  16  and basket arm  20  are rotated by a rotation mechanism  46 . If the basket  16  were not rotated, gas produced during reactions in the solution  14  would form in pockets around the devices  26 . As a result, the pockets would prevent the solution  14  from contacting all of the material to be hydrolyzed and could potentially lead to explosive gas mixtures within the solution  14 . Further, without basket rotation, the reactants in the solution  14  may be depleted locally around material to be hydrolyzed. However, rotation of the basket ensures that no local depletion in the solution  14  occurs. For the present invention, the basket  16  is rotated until all of the energetic material  27  is rendered non-energetic. 
     As further shown in  FIG. 1 , the system  10  provides for mixing the solution  14 . Specifically, a mechanical agitator  48 , jets  50 , and/or a recirculation pump  52  in fluid communication with the solution  14  via recirculation line  54  are provided to mix the solution  14 . As is also shown, the system  10  includes an effluent removal line  56  for the removal of used caustic or non-gaseous products of the reactions within the solution  14 . In order to neutralize the effluent, the removal line  56  delivers the effluent to a treatment device  58  where the effluent may be oxidized, neutralized, or otherwise modified to a less hazardous form. Alternatively, the solution  14  may be reused for subsequent batches of devices  26 . Importantly, the porosity of the basket  16  allows for reuse of the solution  14 , if desired, since it keeps solid contaminants within the basket  16  while the solution  14  drains out of the basket  16 . 
     For the present invention, the system  10  further provides for post-reaction treatment of the components remaining in the basket  16 , i.e., the materials not reactive to the solution  14 . Specifically, the system  10  includes a rinse fluid  60  that is held within a container  62 . Further, the lifting arm  18  is adapted to remove the basket  16  from the tank  12  and to immerse the basket  16  in the rinse fluid  60 . As during the reaction process, the basket arm  20  is able to rotate or revolve the basket  16  within the rinse fluid  60  to rinse off the non-reactive components remaining in the basket  16 . After the components are thoroughly rinsed, the basket  16  is withdrawn from the rinse fluid  60  and is unloaded. 
     As shown in  FIG. 1 , the assembled devices  26  initially enclose the energetic material  27  (shown in  FIG. 2 ) so that it is not exposed to the solution  14  when the basket  16  is submerged. By avoiding the requirement that the devices  26  be preprocessed to provide access to the energetic material  27 , the likelihood of accidental initiation of the energetic material  27  is significantly decreased. With that in mind, for the present invention, the devices  26  are positioned in the basket  16  and introduced to the solution  14  while still completely enclosing the energetic material  27 . Typically, the devices  26  are formed from aluminum or other materials that are attacked by the solution  14 . During the reaction between the solution  14  and the devices  26 , the solution  14  corrodes the devices  26 . Eventually, the solution  14  penetrates the devices  26  and contacts and reacts with the energetic material  27 . As shown in  FIG. 2 , the solution  14  has partially corroded device  26 ′ and contacted the energetic material  27 . Specifically, the wall  29  of the device  26 ′ has been breached and energetic material  27  is exposed. For devices  26  made from materials that are impervious to the solution  14 , such as stainless steel, then a path of entry for the solution  14  must be made prior to use of the system  10 . 
     Referring now to  FIG. 3 , the operation of the system  10  of the present invention is illustrated. As shown in  FIG. 3 , the method commences with the step of positioning the assembled devices in the porous basket (action block  100 ). As discussed above, the assembled devices need not be pretreated or preprocessed to expose the energetic material within the devices. After the devices are received in the porous basket, the basket is closed and is completely submerged in the caustic solution held in the tank (action block  102 ). 
     Complete submersion of the basket ensures that the solution maintains its moderating effect on the energetic material. If the basket or tank emerges from the solution before the energetic material is rendered non-energetic, the heat of hydrolysis can ignite or detonate the energetic material. Further, if the energetic material emerges from the solution, it may adhere to the tank or another device component. After it is submerged, the basket is rotated in the solution to facilitate a reaction between the assembled devices and the caustic hydrolysis solution. For the present invention, rotation of the basket prevents the formation of pockets of gas on the devices and ensures that all surfaces of the devices are contacted with the caustic solution (action block  104 ). 
     While the basket is submerged and rotated, the reaction rate between the device, energetic material and caustic solution is controlled (action block  106 ). Specifically, the reaction rate may be controlled by manipulating the temperature of the solution by selectively adding heat thereto or removing heat therefrom. Alternatively or additionally, the reaction rate may be controlled by selectively increasing and decreasing the surface area of the caustic hydrolysis solution to control the temperature of the solution. For either method, the caustic hydrolysis solution is preferably kept between approximately 60° C. and approximately 130° C. 
     As shown in action block  108 , the method further includes the step of mixing the solution. In practice, the solution may be mixed by a mechanical agitator in the tank, by forcing fluid into the tank via jets, or by recirculating the solution through the tank. 
     When the energetic material has fully reacted and is rendered non-energetic, the basket is removed from the solution (action block  110 ) by the lifting arm. The lifting arm then immerses the basket in the rinse fluid (action block  112 ). While in the rinse fluid, the basket is revolved in order to rinse off any components remaining in the basket (action block  114 ). Thereafter, the basket is withdrawn from the rinse fluid (action block  116 ) and any remaining components are unloaded from the basket (action block  118 ). The remaining components, such as unreacted non-energetic remnants of the devices may be recovered and recycled. 
     As further shown in  FIG. 3 , the method may also include the step of diluting the hydrogen in the off gases with air to ensure that the hydrogen level is below the explosive limit (action block  120 ). Further, the condensable components of the off gases may be removed from the off gases by condensation (action block  122 ). Thereafter, the condensates, such as water, may be returned to the hydrolysis solution in the tank (action block  124 ). Further, the method may include the step of expelling gases from the hood (action block  126 ). Specifically, gases may be expelled through the vent in the hood in order to maintain desired conditions in the hood. Likewise, effluent may be removed from the tank (action block  128 ) and neutralized (action block  130 ) for further uses or safe disposal. As a result of the system&#39;s control over the solution, gases, condensate, and effluent, the tank of solution may be reused, repeating the above steps with another batch of assembled devices. 
     While the particular Hydrolysis System and Process for Devices Containing Energetic Material as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.