Effect of reburning temperature on physico-chemical characteristics evolution of rice husk char

Different kinds of rice husk (RH) char were prepared in an entrained flow reactor under reburning conditions. The physico-chemical properties of pyrolyzed RH chars were characterized by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), specific surface area and pore size analyzer, X-ray diffraction (XRD) and Fourier transform infra-red (FT-IR) spectroscopy, respectively. The effects of temperature on evolution of physico-chemical structures of RH chars were discussed. The results indicate that the specific surface area and pore volume of RH chars increase significantly from 850 to 1 150 ℃. The order of release of alkaline and alkaline earth metals (AAEMs) bound in RH is Na > Ca > Mg > K. With increasing reaction temperature, release fractions of AAEMs generally increase firstly and then being stable, and the chlorine release fraction increases gradually. AAEMs in RH chars are mainly in the form of silicate and sulfate. The surface oxygen-containing functional groups in RH chars decrease significantly with increasing temperature.