Transformation characteristics of sodium in Zhundong coal under circulating fluidized bed gasification

In this study, the transformation characteristics of sodium in Zhundong coal were investigated during oxygen-rich gasification in a circulating fluidized bed (CFB) reactor. The reactor, with a fuel treatment rate of 0.4 t/d, was specially made for experiments on thermochemical conversion of high alkali coal. The equilibrium distribution of sodium in an oxygen-rich atmosphere with water steam was predicted by thermodynamic equilibrium calculations. Sodium in the ash increased with the injection of water steam and the increase in O2 concentration in the gasification agent; accordingly, less sodium was released in the gaseous phase. Sodium existed mainly as NaAlSiO4 in the bottom ash, and as NaCl and NaAlSiO4 in the fly ash. With the injection of water steam and the increased O2 concentration, the NaAlSiO4 content increased markedly. No slag phase of sodium was found in either the experimental study or the equilibrium calculation. It is beneficial to inhibit slagging and fouling in the CFB reactor during the oxygen-rich gasification with water steam.