The aim of this work was to optimize the parameters involved during incineration of burnable, often strongly chlorinated, radioactive wastes. This process includes two steps: pyrolysis at 550°C and plasma post-combustion at 1400°C with an excess of oxygen.
CEA/.../SCD has developed a pilot-scale reactor using a plasma torch to burn the gases produced by a rotary kiln pyrolyzer. The tubular reactor is the evaporator of a heat transfer system ensuring both removal of the heat flux and control of the wall temperature (between 200 and 400°C) to prevent condensation. Efficiency of the concept and reliability of the pilot have been proved by several long time trials.
In order to control or to predict the composition of the exhaust gases, a model previously developed with a C/H/O/N system, has been extended to chlorinated and fluorinated wastes. This model is based on calculation of chemical kinetics inside the post-combustion plasma reactor. The temperature evolution along the cylindrical afterburner chamber is deduced from calorimetric balances and from thermocouples.
More than fifty species and two hundred reactions, direct and reverse, have been taken into account in the following chemical system: Ar/C/H/O/N/Cl/F.
Model predictions have been compared with off-gas analysis results, concerning especially CO, NOx and chlorine compounds.