The technology and equipment developed in this project addresses the substantial waste stream associated with the annual manufacture of millions of pounds of energetic materials for Department of Defense (DoD) use. The objective of this project was to develop a manufacturing process enabled by a Continuous Acoustic Mixer (CAM) using technology that reduces the waste stream and improves worker safety when processing rocket propellants, explosives and pyrotechnic formulations for DoD munitions.
A prototype CAM device was redesigned to improve Clean-In-Place (CIP) capabilities (referred to as the CAM-CIP) based on ResonantAcoustic® Mixing (RAM) technology that was repeatedly demonstrated to be the superior mixing technology for processing energetic materials. The CAM-CIP realized these same advantages while enabling continuous manufacturing of energetic material using a RAM environment. The CAM-CIP was also designed to allow for temperature control of the mixed material and rated for mixing energetic material.
A surrogate energetic formulation was developed by Naval Air Warfare Center Weapons Division (NAWCWD) China Lake to simulate the viscosity and density of a standard plastic-bonded explosive (PBX) used by the US Navy. The surrogate formulation was also developed with water insoluble materials to accurately reflect the PBX material behavior during a CIP process.
The continuous mixing and CIP processes were characterized on the prototype CAM-CIP system using measurements of the produced material’s density, solids composition, maximum stress, maximum strain, and hardness. The knowledge gained from the characterization was used to model the mixing and CIP behavior, and the models were used to design and manufacture an energetics rated CAM-CIP with temperature measurement and control capability.
The new energetics rated CAM-CIP was characterized and optimized to produce surrogate energetic material at a maximum rate of 3 kilogram/minute while providing good homogeneity and consistency. The CAM-CIP produced a significantly reduced waste stream (both volume and toxicity) during production and cleaning. The CAM-CIP also resulted in improved operator safety. The key is the reduced CAM volume (surface area requiring cleaning) relative to batch mixing vessels, and the ability of the RAM environment to enable limited amounts of soap and hot water (not volatile or hazardous solvents) to effectively clean the mixing components.
The next phase of the project was to transition the CAM-CIP equipment and knowledge to NAWCWD China Lake to produce high energy formulations used by the DoD. Ultimately, this effort would quantifiably answer the questions as to the extent to which the implementation of the CAM-CIP system would reduce environmental, safety and occupational health impacts associated with the large scale manufacturing of energetic formulations. It was anticipated that implementation of the CAM-CIP technology would significantly reduce downstream waste produced in current batch production operations.
The CAM-CIP technology will benefit the DoD by providing a functional, cost effective, scalable mixing process and methodology for manufacturing energetic formulations that will reduce energetic material waste, cleaning waste, solvent use, water use, and energy use in manufacturing.