The global objective of this study is to reduce the NOx and CO emissions during the incineration of solid fuels in grid system furnaces. To rich this objective, we choose a typical molecule of plastic : the polyamide-6,6. The interest of this molecule is double : it has a lot of applications (textile, pieces done by molding,...) and it contains some nitrogen. Knowing that during incineration, the main part of the NOx emitted (more than 80%) is formed according to the fuel NOx mechanism, the study of the combustion of polyamide allows to improve our knowledge on the NO formation from this technology. To optimize the combustion and to reduce the pollutants formation, we study first the thermal decomposition of the polyamide-6,6, with a particular following of the nitrogen atoms becoming, and, secondly, we use these results to adjust the parameters of combustion during the incineration process to limit the NOx emissions. Two different experimental setups were built. The first one is used to study the thermal decomposition of the molecule for various conditions : pyrolysis or combustion, various residence times (from 0.3 to 2s) and temperatures (800 and 1000 degreesC). During the pyrolysis, the main part of the nitrogen is emitted as HCN and NH3. The HCN efficiency is directly dependant of the temperature and the residence time, when the NH3 part still the same whatever the conditions tested. In condition of combustion, about 12% of the nitrogen is transformed into NOx. The second device is then used to simulate the process of combustion in an industrial furnace of incineration, and allows to determine some optimum conditions of combustion to reduce the NO emissions without increasing the CO emissions. An important reduction of NO emissions had been obtained, and for the best conditions, only 2.5% of the nitrogen contained in the solid is transformed into NO. Moreover, the tendencies observed on our pilot are directly transposable to industrial furnaces.
