The release of sodium during biomass gasification and pyrolysis in fluidized bed was systematically investigated based on an on-line measurement system. The temperature and atmosphere had strong influences on sodium release behavior. The pyrolysis atmosphere was conducive to the release of sodium than the CO2 gasification atmosphere at 900 degrees C. The overall kinetic parameters of sodium release during two thermal conversion processes were obtained based on the experimental results of instantaneous sodium concentration in flue gas and inverse method. Furthermore, the influence of chlorine on sodium release was studied based on the on-line measurement system. The promoting effect of chlorine on Na release in CO2 gasification was much more obvious than pyrolysis. Thermodynamic equilibrium calculations were conducted to identify the sodium species during biomass gasification and pyrolysis. The formation of Na2CO3 (s, l) mainly accounted for the lower release percentage of sodium in CO2 gasification than pyrolysis. (C) 2016 Elsevier Ltd. All rights reserved.