The reapplication of energetic materials as boiler fuels

Decommissioning of weapons stockpiles, off-specification production, and upgrading of weapons systems results in a large amount of energetic materials (EM) such as rocket propellant and primary explosives that need to be recycled or disposed of each year. Presently, large quantities of EM are disposed of in a process known as open-burn/open-detonation (OB/OD), which not only wastes their energy content, but may release large quantities of hazardous material into the environment. Here the authors investigate the combustion properties of several types of EM to determine the feasibility of reapplication of these materials as boiler fuels, a process that could salvage the energy content of the EM as well as mitigate any potential adverse environmental impact. Reapplication requires pretreatment of the fuels to make them safe to handle and to feed. Double-base nitrocellulose and nitroglycerin, trinitrotoluene (TNT), nitroguanidine, and a rocket propellant binder primarily composed of polybutidiene impregnated with aluminum flakes have been burned in a 100-kW downfired flow reactor. Most of these fuels have high levels of fuel-bound nitrogen, much of it bound in the form of nitrate groups, resulting in high NO{sub x} emissions during combustion. The authors have measured fuel-bound nitrate conversion efficiencies to NO{sub x} of up to 80%, suggesting that the nitrate groups do not follow the typical path of fuel nitrogen through HCN leading to NO{sub x}, but rather form NO{sub x} directly. They show that staged combustion is effective in reducing NO{sub x} concentrations in the postcombustion gases by nearly a factor of 3. In the rocket binder, measured aluminum particle temperatures in excess of 1700{degrees}C create high levels of thermal NO{sub x}, and also generate concern that molten aluminum particles could potentially damage boiler equipment. Judicious selection of the firing method is thus required for aluminum-containing materials