The influence of NaCl and Na2CO3 on fine particulate emission and size distribution during coal combustion

This research focuses on the effects of NaCl and Na2CO3 sodium additives on fine particulate emission and size distribution. The experiment was conducted in a drop tube furnace under typical power plant conditions. Particulate emissions were measured by an electrical low pressure impactor (ELPI+). NOX emissions were studied using a Testo350 flue gas analyzer. Both NaCl and Na2CO3 sodium additives have been shown to reduce NOX emissions during coal combustion. Sodium additives also increased the amount of ultrafine particulate matter (PM0.1), especially, PM with an aerodynamic diameter (Da) in the 0.0212 μm-0.0561 μm range increased significantly. NaCl and Na2CO3 will affect the emission of fine PM (PM10) through different mechanisms. NaCl was prone to vaporization when it was added to furnace. Gas-phase Na will generate Na2SO4/Na2SiO3 vapor followed by nucleation/condensation. Increasing the Na/N ratio increased the number of particles and the mass-concentration of submicron PM (PM1), but had little effect on the concentration of PM1∼10. Alternatively, Na2CO3 mostly produced PM greater than 10 μm in Da via a breakage/melt-agglomeration process. A small portion of the Na2CO3 reacted to generate NaCl and influence the submicron PM. As the Na/N ratio increased, the amount of PM less than 0.1 μm in Da (PM0.1) and PM between 1 μm and 10 μm in Da (PM1∼10) decreased.