On-line measurement and kinetic studies of sodium release during biomass gasification and pyrolysis

• Temporal release of sodium from sawdust gasification and pyrolysis was measured.
• Influences of temperature and atmosphere on sodium release were investigated.
• Chlorine was more propitious to sodium release in gasification than pyrolysis.
• Thermodynamic equilibrium calculations were conducted to identify sodium species.

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 °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.