Patent Application
20130014866
1. Field of the Invention
The invention relates to methods for recovery and separation of high explosive from aged munitions and more particularly to a method for reclaiming a high explosive from warhead by melting-out in supercritical fluid.
2. Description of Related Art
How to effectively remove obsolete and aged munitions and explosive inventories from the active arsenal in a safe manner is of great concern. Typically, demilitarization programs focused on disposal or destruction. Recently, there have been efforts to develop recycling and/or reclamation processes that permit explosives and higher valued constituents of munitions systems to be recovered and re-used in military applications due to environmental protection.
Typical methods for extracting TNT from high explosives include melting out of and steaming out of the explosive from the projectile casing. These two methods are disadvantageous for being time consuming, inappropriate for mass reclamation of TNT, generating too much polluted waste water which is required to treat in prohibitively high cost, and being low efficiency.
U.S. Pat. No. 5,953,679 to Morris discloses a method for the extraction of TNT from a high explosive comprising contacting the high explosive with a supercritical fluid at a temperature above the melting temperature (e.g., 85 degrees Celsius) of TNT and at a pressure (e.g., 37.4 MPa) sufficient to extract the TNT. However, it is known that there are other explosive components in the high explosive. Thus, it is very possible that unexpected explosions may occur during the extraction. This is very dangerous.
It is also known that many explosive components have a very low solubility in carbon dioxide based supercritical fluid. Further, TNT has a very low solubility in carbon dioxide based supercritical fluid. Thus, a great volume of carbon dioxide based supercritical fluid is required for reclaiming TNT from the high explosive. This in turn adversely increases the cost.
Notwithstanding the prior art, the invention is neither taught nor rendered obvious thereby.
It is therefore one object of the invention to provide a method for the retraction of an explosive component from a high explosive, comprising the steps of loading a high explosive containing an explosive component into a melting-out vessel; supplying a supercritical fluid to the melting-out vessel; and contacting the high explosive with the supercritical fluid at a temperature below the melting point of the explosive component and at a pressure sufficient to melt-out the explosive component.
In a first aspect of the invention, the explosive component is at least one of TNT and TNT-based high explosive.
In a second aspect of the invention, the TNT-based high explosive is selected from the group consisting of Comp B, Amatol, Octol, and Ammonal.
In a third aspect of the invention, the temperature is between about 50 and 75 degrees Celsius and the pressure are between about 15 and 40 MPa.
In a fourth aspect of the invention, the temperature is about 55 degrees Celsius and the pressure is about 25 MPa in optimum conditions.
In a fifth aspect of the invention, the explosive component melt-out from the warhead has at least 99%.
By utilizing the invention, the following advantages and benefits are obtained: Safety because the carbon dioxide as a supercritical fluid is employed at a temperature less than the melting point of TNT. It is an environmentally friendly method because no organic solvent is used for collection purpose. Carbon dioxide can be substantially completely recycled after the melt-out. Hence, no pollution is generated. Cost effectiveness because the method is time saving and batch based. The TNT melt-out is done in a melting state, resulting in an increase of the percentage of TNT being melted-out.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings.
Temperature and pressure at the critical-point are defined as the critical temperature (TC) and critical pressure (PC). The critical parameters for carbon dioxide are TC first 31 degrees Celsius and PC first 7.39 MPa. A supercritical fluid results when the temperatures and pressures of the materials are greater than their critical parameters. For effective melt-out of high explosive, operation is done at pressure of about 25 MPa and temperature of about 55 degrees Celsius. All high explosive melt-out were carried out using a carbon dioxide based supercritical fluid in a safe and cost effective manner because the liquid carbon dioxide is non-flammable, non-toxic, chemically stable, and cost effective.
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Following are examples of the invention with the space 511 having a volume of two (2) liters:
A simulated warhead of 40 mm diameter containing 60 g TNT in an inverted position is held by a support. Place both the support and the warhead in a melt-out vessel prior to sealing. TNT begins to melt from the warhead as pressurized liquid carbon dioxide as a supercritical fluid is supplied to the melt-out vessel. Percentages of the melted TNT are tabulated in the following Tables (I) and (II) as temperature and pressure vary in the melt-out operation which takes about 30 minutes.
A simulated warhead having a volume of 250 ml containing 250 g TNT in an inverted position is held by a support. Place both the support and the warhead in a melt-out vessel prior to sealing. TNT begins to melt-out from the warhead as pressurized liquid carbon dioxide as a supercritical fluid is supplied to the melt-out vessel which is maintained at a temperature of about 55 degrees Celsius and at a pressure of about 25 MPa. The melt-out operation takes about 30 minutes. Results: About zero (0) gram TNT is remained in the warhead and about 241 g of TNT is collected in the TNT collection vessel after the melt-out operation.
A simulated warhead having a volume of 350 ml containing 500 g TNT in an inverted position is held by a support. Place both the support and the warhead in a melt-out vessel prior to sealing. TNT begins to melt-out from the warhead as pressurized liquid carbon dioxide as a supercritical fluid is supplied to the melt-out vessel which is maintained at a temperature of about 55 degrees Celsius and at a pressure of about 25 MPa. The melt-out operation takes about 30 minutes. Results: About zero (0) gram TNT is remained in the warhead and about 490 g of TNT is collected in the TNT collection vessel after the melt-out operation.
A 105 mm howitzer warhead containing 2200 g composition B (i.e., Comp B) consisting of 60% RDX, 40% TNT, and less than 1% wax in an inverted position is held by a support. Place both the support and the warhead in a molt-out vessel prior to sealing. Composition B begins to molt-out from the warhead as pressurized liquid carbon dioxide as a supercritical fluid is supplied to the molt-out vessel which is maintained at a temperature of about 65 degrees Celsius and at a pressure of about 25 MPa. The melting-out operation takes about 120 minutes.
A 155 mm howitzer warhead containing 6700 g TNT in an inverted position is held by a support. Place both the support and the warhead in a molt-out vessel prior to sealing. TNT begins to molt-out from the warhead as pressurized liquid carbon dioxide as a supercritical fluid is supplied to the molt-out vessel which is maintained at a temperature of about 65 degrees Celsius and at a pressure of about 25 MPa. The melting-out operation takes about 30 minutes.
It is envisaged by the invention that the optimum temperature and pressure for melting-out TNT from a warhead are 55 degrees Celsius and 25 MPa respectively. The 55 degrees Celsius is less that the melting temperature of 80 degrees Celsius of TNT and the 25 MPa is less than the required pressure of 27.4 MPa respectively as compared with the conventional method of extracting TNT from a warhead. Hence, the invention is both safer and more cost effective as compared with the conventional TNT extraction method.
It is also envisaged by the invention that in the process of melting-out TNT from Comp B (as another high explosive) more than 99% TNT contained in the warhead can also be melted-out as mentioned above. Alternatively, the high explosive of the invention can be selected from the group consisting of Amatol, Octol, and Ammonal. While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.
