Currently, the U.S. Department of Defense (DoD) has no method of recovering highly valuable energetics, such as HMX and RDX, from obsolete, reject or surplus Class 1.1 propellants and explosives. Many munitions items (including projectiles, missile and torpedo warheads, and strategic rocket motors) contain significant quantities of these energetic compounds. Current open burning/open detonation (OB/OD) destruction practices release hazardous pollutants into the environment and negate the value of these products. This project demonstrated a new process for extraction and recovery of HMX and RDX from warheads and other projectiles using common mineral acids instead of organic solvents, thereby eliminating the need for disposal of hazardous organic wastes
A single, pilot-scale, batch facility (150 pounds per day) was constructed at Fort Wingate Army Depot in Gallup, NM and demonstrated between March 21-25, 1999, to chemically extract and mechanically reprocess HMX from LX-14 and RDX from Composition A-3. The process involved solubilizing or melting the explosives' binders with either acid (for LX-14) or hot water/surfactant (for Composition A-3), then separating the explosive from the binder solution by centrifugation. The average batch processing time for HMX and RDX recovery were 24 hours and 6 hours, respectively. The recovered explosives were of high purity (98 percent or better) and yield (96 percent or better), with melting point and physical appearance comparable to those of pure HMX and RDX.
The capital cost for the 150 pounds per day batch plant was estimated at $1.34 million. HMX could be recovered from LX-14 at a savings of $9.75 per pound after its sale for reuse, compared to conventional disposal by OB/OD. The payback was 3.6 years and the Internal Rate of Return over 15 years was 30 percent, when the dual benefits of material sales and the avoidance of the cost of OB/OD were considered. However, the process was not economically viable for RDX recovery due to the low market price for RDX. Also, waste reagents from LX-14 processing can be evaporated into a valuable ammonium nitrate/polymeric fuel, which can be used as a blasting agent and has been formulated with a granular plastic bonded explosive to make a unique metal bonding explosive BondEx A™. The estimated capital cost for a 500 pounds per day plant, which would give more economies of scale, was $3.87 million.
This technology will reduce or eliminate the cost of demilitarization for munitions items containing HMX, such as the Hellfire and Tow missile warheads, and will allow recycling of HMX scraps, surplus and obsolete material. The reduced cost of recovered HMX would make it feasible for the DoD to use HMX in many munitions that do not meet Insensitive Munitions requirements. These include the replacement of Composition B in PBXN-110 and, for the Department of Energy, the use of this alternative domestic source of HMX in PBX-9501.