Fire properties of refuse-derived fuels: measurements of temperature profiles and mass loss

This investigation constitutes part of a larger study designed to obtain insights into fire properties of refuse-derived fuel (RDF). Several fires of densified RDF occurred in silos storing this material, giving us an impetus for this study, with the present investigation focusing on measuring temperature profiles and mass loss of RDF samples. A specialised sample holder was constructed to accommodate four fine thermocouples (76 μm in diameter), which facilitated the measurement of the temperature profiles within RDF samples undergoing oxidation and pyrolysis. An additional thermocouple was positioned at the base of the sample to verify the assumption of heat transfer in semi-infinite slab, prior to ignition. This assumption was applied previously within the context of the integral analysis to obtain the value of the effective thermal conductivity. The temperature profiles prior to ignition were combined with the measurements of the surface temperature collected by a pyrometer. Mass-loss measurements were also performed, but only after the onset of the flaming combustion, as a consequence of fluctuations induced by the changing flow field above the samples. A separate data-acquisition system was used to allow a faster sampling rate than 1 Hz permitted by the default setting of the cone calorimeter. The experiments determined the critical mass flux at extinction and identified three combustion regimes occurring in fires of RDF-type materials: flaming combustion; a transition regime involving simultaneous flaming combustion and char pyrolysis; and char pyrolysis. These measurements were consistent with results of the earlier fire experiments performed in the cone calorimeter.