Examination of inorganic gaseous species and condensed phases during coconut husk combustion based on thermodynamic equilibrium predictions

Multi-component thermodynamic equilibrium predictions of coconut husk combustion products were performed in this work. The calculation results showed that the concentration of the chlorine species in the flue gas and ash were clearly influenced by the combustion temperature. At temperatures below 820 °C the highest concentration was HCl(g), and above 820 °C was KCl(g). Chlorine species were also observed in ash, as KCl–NaCl–RbCl solid solution (when the combustion temperature was lower than 700 °C), and KCl–NaCl–K2SO4–Na2SO4 liquid solution (in the range of 600–960 °C). At low combustion temperatures (600 °C), chlorine retention in solid ash was the most effective. Speciation of inorganic gaseous species and condensed phases were investigated also during flue gas cooling from 1000 to 200 °C. Major condensed phase compositions were dominated by alkali metal salts in both solid and liquid phase states. In addition, the Gibbs energy of substance formation, and Gibbs reaction energy, in order to thoroughly interpret the thermodynamic predictions were determined. Finally, thirty seven eutectic points for binary systems calculated in the “Phase Diagram” module of the FactSage package were presented. For the purposes of interpreting the results, the melting point ranking for pure substances and binary systems were created.