Condensation behaviors of alkali salt vapors in biomass combustion

Based on the release characteristics of potassium, chlorine and sulfur during biomass combustion, the condensing behavior of pure potassium chloride vapors and alkali salt vapors from biomass under different wall temperature was studied in laboratory. The results showed that the total release of potassium could reach 93%, while chlorine and sulfur were almost completely removed from biomass when the temperature exceeded 815℃ and 1100℃, respectively. The pure potassium chloride vapors adhered to the substrate surface of different temperature (400℃, 520℃ and 600℃) through two mechanisms, including condensation to deposition and fusion to adhesion. The depositing rate of pure potassium chloride vapors on the substrate surface of 520℃ was 7.2×10^-5 g/min, with the appearance of elongate crystals like dendrites, significantly higher than that of 4.97×10^-5 g/min of pure potassium chlorine vapors on the substrate surface of 400℃. The matter containing potassium was not found on the surface during low temperature combustion. But the potassium chloride crystals could be found when the combustion temperature exceeded 800℃, whose sticking mechanism is the same as that of pure potassium chloride vapors.