The batch processing method currently used to produce nitramine propelling charges for Low Vulnerability Ammunition (LOVA) at the Indian Head Division of the Naval Surface Warfare Center utilizes Volatile Organic Compounds (VOC), which are released untreated into the atmosphere as hazardous emissions. This conventional method typically releases one pound of solvent per three pounds of propellant produced. The objective of this project was to demonstrate the ability of the Closed Loop Energetics with VOC Emission Reduction (CLEVER) process configuration to cost-effectively produce acceptable propellant while significantly reducing VOC hazardous waste emissions.
There are two sequential steps in the closed-loop CLEVER process. The first step, developed by the Nobel Chemicals branch of Bofors in Sweden, is a closed-loop process involving dissolution of energetic ingredients and plasticizers into ethyl acetate solvent, steam precipitation of the propellant powder, and evaporation of solvents for recovery and recycle. In the second step, the dried propellant powder is re-processed in a twin-screw extruder for final extrusion and cutting.
Two small lots of EX-99 propellant grains were produced for testing in the new Extended Range Guided Munitions (EGRM) round for the Navy 5-inch gun. The CLEVER process reduced VOC emissions by 47 percent and hazardous scrap solid waste propellant by 50 percent, while reducing labor and material costs by 41 percent. Propellant paste and grains passed all required tests for chemical composition, physical and mechanical stability, and safety. Both lots of propellant produced during the demonstration were also successfully gun-fired. Ballistic performance as measured by muzzle energy, chamber pressure, and velocity variation were outstanding, as good or better than any other test propellant produced to date.
The capital cost for a 250,000 pounds per year plant at Indian Head was estimated to be $11 million with a discounted payback period of 5.15 years. An additional benefit would be a reduced load on the Thermal Catalytic Incineration System (TCIS), which was mandated by regulators from the state of Maryland to destroy emissions from the existing process. The Navy has awarded contracts to implement the CLEVER process at Indian Head Division. The plant should be operational by fiscal year 2004.