Speciation of inorganic gaseous species and condensed phases during coconut husk combustion based on thermodynamic equilibrium calculations

Abstract

Thermodynamic equilibrium calculations to predict coconut husks (CH) combustion products have been carried out in this work. The selected type of biomass belongs to problematic fuels due to the fibrous structure preventing its grinding, and high chlorine content. The calculations results showed, that the combustion temperature for the tested range of 600-1000°C clearly affects the concentrations of chlorine species in the flue gas. When the temperature was below 820°C, the highest concentration had HCl(g), and above 820°C KCl(g). The chlorine was also present in ash, as KCl-NaCl-RbCl solid solution, when the combustion temperature T <700°C, and KCl-NaCl-K2SO4-Na2SO4 liquid solution, when 600 <T <960 °C. High content of chlorine in ash from CH combustion at T = 650°C has been confirmed experimentally. Speciations of inorganic gaseous species and condensed phases we investigated also during flue gas cooling from 1000 to 400°C. Major condensed phase composition were dominated by alkali metal salts in both solid and liquid phase states. Finally, we presented sixteen eutectic points for different binary systems calculated in the FactSage software.