Physical and chemical properties of fly ash from fluidized bed gasification of Zhundong coal

The ash fusion characteristics, physical structure, chemical compositions and gasification reactivity of Zhundong coal (ZD) fly ash from fluidized bed gasification were explored by fusion point analyzer, X-ray fluorescence spectrometer (XRF), scanning electron microscopy (SEM), and thermo-gravimetric analyzer. The results show that the concentrations of minerals in ZD fly ash, such as SiO₂, Fe₂O₃, Na₂O, CaO, change greatly during gasification process, but the ash fusion temperature of ZD fly ash is similar to that of ZD. There is a wide particle-size distribution in ZD fly ash, which shows a significant bimodal distribution, and a large difference of elemental compositions for ZD fly ash of different particle size. The reactivity of ZD fly ash increases with the increase in gasification temperature. Compared with the ZD char from pyrolysis, the ZD fly ash has more advanced carbon crystalline structure, a larger surface area and is relatively rich in meso-pores and macro-pores, which results in a higher gasification reactivity.