Pyrolysis characteristics and kinetic analysis of walnut shell

The pyrolysis of walnut shell was carried out by means of the thermogravimetric method in high pure N2 atmosphere. The influences of different heating rates (5, 10, 20 and 40 K/min) on the pyrolysis process were investigated and the pyrolysis mechanism was discussed. The results show that the non-isothermal pyrolysis process of walnut shell includes three distinct stages: dehydration, fast-pyrolysis and residue slow decomposition. The second stage in which a huge amount of released volatile components caused the distinct weight loss of walnut shell played a main role in the whole process. With the increase of heating rate, the maximum decomposition rate and its corresponding temperatures of walnut shell increase. The TG curve and the peaks in DTG curve shift to higher temperatures due to the aggravating thermal lag. The pyrolysis processes are well described by the models of Jander equation and valid for diffusion control. The activation energies range from 102.28 to 117.73 kJ/mol and the pre-exponential factors vary from 4.13×10⁶to2.42×10⁸ min^-1at different heating rates.