IGNITION AND COMBUSTION OF SINGLE, LEVITATED CHAR PARTICLES

The paper focuses on the experimental measurement and model prediction of burnout times and ignition temperatures of single char particles. Experimental temperature-time histories of single, submillimetric char particles are compared with the predictions of a simple model that lakes into account all the experimental findings obtained on a model char with an electrodynamic balance (EDB). The particular features of the experimental technique, allow the measurement of the temperature of the surface of a single levitated particle as the high temperature reaction proceeds. The particle is heated to reaction conditions with a laser while the surrounding. gases are maintained at room temperature. Particle ignition temperatures and burnout times are easily detected from experimental curves. Even with the high temperature (2500-3000 K) and low characteristic time of the reaction (30-100 ms), reproducible experimental data were obtained, confirming that the EDB is a viable tool for studying high-temperature heterogeneous gas-solid reactions. Experimental results are compared with the predictions of a simple model developed for the description of high temperature combustion of single char particles. Even if particle morphological modifications occurring at high conversion degrees are not accounted for, the model well describes the particle ignition process and predicts with sufficient accuracy ignition temperatures and burnout times.