Influence of carbonization degree of walnut shell char on pore structure and combustion characteristics

The effect of carbonization degree on pore structure and microstructure of walnut shell chars was studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The combustion characteristics of raw material and walnut shell chars were analyzed using a thermogravimetry coupled with differential scanning calorimeter (TG-DSC). The results show that the appropriate degree of carbonization (volatile content is 6%-15%) leads to the disorderly crystallization of turbostratic and the increase of defects in the carbonaceous microcrystalline structure, which causes a relatively flourishing pore structure and an increase of specific surface. Pyrolysis char at temperature of 500℃ has the maximum specific surface area of 374.60 m²/g, while walnut shell char prepared at 600℃ has the optimal combustion characteristics with the combustion characteristics index of 7.16×10⁶, which indicate that the appropriate carbonization degree of char could reduce the volatile content and increase the higher calorific value of char during combustion process. Moreover, the developed pore structure can increase the contact area between char and air, leading to the accelerated combustion rate of char.