Study on Mass Transfer of Ash during Bamboo Powder Combustion

Abstract

In this study, mass transfer of ash during bamboo powder combustion on a flat flame is investigated experimentally and numerically. The bamboo powder combustion consisted of volatiles emission, volatiles combustion, char formation, char combustion, and finally ash formation. The mass of ash formed was about 3 wt% that of raw bamboo powder. The mass of ash decreased with the equivalence ratio Φ for flat flame combustion.Part of the ash fused and then adhered to the Inconel mesh for wrapping of bamboo powder as bottom ash, flowing through the mesh. The mass adhered to the Inconel mesh depended strongly on the equivalence ratio Φ. The fusion tendency of the atmospheric oxidization ash agreed qualitatively with Liu's standard bamboo ash fusion test. On the other hand, as ash fusion started locally in this work, it suggests that the concentration of metal oxides of the atmospheric oxidization ash was not uniform. For the atmospheric oxidization ash at 600 °C, K2Si2O5, KAlSiO4, Na2CaP2O7, Mg2SiO4, K2SO4, and Fe2O3 were predicted to be the major eutectic materials. At 1120 °C, only Fe2O3 remained and the liquid components accounted for about 95%. On the other hand, the major eutectic materials for the combustion ashes of Φ = 0.85 and Φ = 1.0 at 1260 °C were MgO and Fe2O3, respectively. Therefore, the predicted eutectic materials of the combustion ash were changed appropriately in comparison with those for the atmospheric oxidization ash because of the fusion and disappearance of some metal oxide components during combustion.