Analysis of the Interactions between Moisture Evaporation and Exothermic Pyrolysis of Hazelnut Shells

Packed-bed experiments are conducted to examine the effects of moisture evaporation on the global exothermicity of hazelnut shell pyrolysis. Percentages typically reached from ambient conditioning (9-12 wt %, dry basis) do not modify the features of the pyrolytic runaway, with respect to bone-dry samples, apart from the obvious temporal delay. In fact, consequent to moderate external heating, moisture evaporation and solid decomposition take place sequentially. Instead, higher moisture contents lower the display of the reaction exothermicity, owing to the simultaneous occurrence of the two processes at different spatial positions. The interaction between the two is also highly dependent upon the thermal severity of the external heating. Finally, induced humidification by wetting small-sized particles (versus steaming), applied to achieve moisture contents above those of ambient conditioning, modifies the sample chemical properties, thus giving only a qualitative valence to the measurements.