Analysis of the thermal decomposition of munitions wastewater

The thermal decomposition of ammonium nitrate (AN) laden munitions wastewater and comparable control samples were studied under air and nitrogen environments at pressures from 0.1 MPa to 10 MPa. The decomposition enthalpies, measured using a Differential Scanning Calorimeter (DSC), and gaseous emissions, measured using a Fourier-Transform Infrared Spectrometer (FTIR), were used to evaluate the quality of decomposition. Experiments demonstrated that higher pressures improved the energy yield and reduced the quantities of harmful NOx ${{\rm N}{{\rm O}}_{{\rm x}}}$ from the decomposition of all samples. At 10 MPa, experimentally measured decomposition enthalpy from the munitions wastewater was 1.8 MJ/kg, approximately 45 % of its standard enthalpy of decomposition, and NO and NO2 ${{\rm N}{{\rm O}}_{2}}$ accounted for only 0.7 % and 0.08 % of the nitrogen in the sample, respectively. The emissions stream from the wastewater was found to primarily consist of N2 ${{{\rm N}}_{2}}$, CO2 ${{\rm C}{{\rm O}}_{2}}$, H2O ${{{\rm H}}_{2}{\rm O}}$ and N2O ${{{\rm N}}_{2}{\rm O}}$. An analysis of the heat releases and the emissions showed that higher pressures improved the extent and enthalpy of decomposition by preventing premature loss of gaseous intermediates and sensible heat through the pin-hole crucibles used in the experiments. Moreover, high pressures precluded the evaporation of water and promoted the decomposition of AN via a radical mechanism. image