Synergistic effect of physicochemical properties and reaction temperature on gasification reactivity of walnut shell chars

In this study, the physicochemical properties of biochars derived from different pyrolysis temperatures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscope (SEM). The gasification reactivity of biochars and composition of gas products were investigated by thermogravimetric analyzer (TGA) and a lab-scale tube furnace. The results manifested that the carbonization degree and order degree of biochars strengthened by increasing pyrolysis temperature. Thermogravimetric analysis and kinetic parameters indicated that biochar treated by 400 degrees C had the optimal gasification reactivity and required the minimum activation energy to surmount energy barrier for initiating reaction. Moreover, the gas chromatograph further found that pyrolysis temperature of 400 degrees C corresponded to the maximum carbon monoxide yield. At the same time, it also illustrated that the gasification temperature higher than 1000 degrees C would hamper the enhancement of biochar gasification reactivity. More importantly, the volume fraction of CO produced by walnut shell chars was not related to the volatile content, but to the microcrystalline structure of biochars. The crystallite diameter and order degree of biochars showed a strong linear relationship with the volume fraction of carbon monoxide.